Point at lint name instead of whole attr for gated lints

```
warning: unknown lint: `test_unstable_lint`
  --> $DIR/warn-unknown-unstable-lint-inline.rs:4:10
   |
LL | #![allow(test_unstable_lint, another_unstable_lint)]
   |          ^^^^^^^^^^^^^^^^^^
   |
   = note: the `test_unstable_lint` lint is unstable
   = help: add `#![feature(test_unstable_lint)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
note: the lint level is defined here
  --> $DIR/warn-unknown-unstable-lint-inline.rs:3:9
   |
LL | #![warn(unknown_lints)]
   |         ^^^^^^^^^^^^^

warning: unknown lint: `test_unstable_lint`
  --> $DIR/warn-unknown-unstable-lint-inline.rs:4:29
   |
LL | #![allow(test_unstable_lint, another_unstable_lint)]
   |                              ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: the `test_unstable_lint` lint is unstable
   = help: add `#![feature(test_unstable_lint)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
note: the lint level is defined here
  --> $DIR/warn-unknown-unstable-lint-inline.rs:3:9
   |
LL | #![warn(unknown_lints)]
   |         ^^^^^^^^^^^^^
```

This is particularly relevant when there are multiple lints in the same `warn` attribute. Pointing at the smaller span makes it clearer which one the warning is complaining about.

compiler/rustc_lint/src/levels.rs

@@ -915,7 +915,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
 
                 let src = LintLevelSource::Node { name, span: sp, reason };
                 for &id in ids {
-                    if self.check_gated_lint(id, attr.span(), false) {
+                    if self.check_gated_lint(id, sp, false) {
                         self.insert_spec(id, (level, src));
                     }
                 }

tests/rustdoc-ui/lints/feature-gate-rustdoc_missing_doc_code_examples.stderr

@@ -1,8 +1,8 @@
 error: unknown lint: `rustdoc::missing_doc_code_examples`
-  --> $DIR/feature-gate-rustdoc_missing_doc_code_examples.rs:4:1
+  --> $DIR/feature-gate-rustdoc_missing_doc_code_examples.rs:4:10
    |
 LL | #![allow(rustdoc::missing_doc_code_examples)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `rustdoc::missing_doc_code_examples` lint is unstable
    = note: see issue #101730 <https://github.com/rust-lang/rust/issues/101730> for more information

tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.stderr

@@ -1,8 +1,8 @@
 warning: unknown lint: `multiple_supertrait_upcastable`
-  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:3:1
+  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:3:9
    |
 LL | #![deny(multiple_supertrait_upcastable)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `multiple_supertrait_upcastable` lint is unstable
    = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable
@@ -10,10 +10,10 @@ LL | #![deny(multiple_supertrait_upcastable)]
    = note: `#[warn(unknown_lints)]` on by default
 
 warning: unknown lint: `multiple_supertrait_upcastable`
-  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:5:1
+  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:5:9
    |
 LL | #![warn(multiple_supertrait_upcastable)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `multiple_supertrait_upcastable` lint is unstable
    = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable

tests/ui/feature-gates/feature-gate-non_exhaustive_omitted_patterns_lint.stderr

@@ -1,8 +1,8 @@
 warning: unknown lint: `non_exhaustive_omitted_patterns`
-  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:3:1
+  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:3:9
    |
 LL | #![deny(non_exhaustive_omitted_patterns)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `non_exhaustive_omitted_patterns` lint is unstable
    = note: see issue #89554 <https://github.com/rust-lang/rust/issues/89554> for more information
@@ -11,10 +11,10 @@ LL | #![deny(non_exhaustive_omitted_patterns)]
    = note: `#[warn(unknown_lints)]` on by default
 
 warning: unknown lint: `non_exhaustive_omitted_patterns`
-  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:5:1
+  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:5:10
    |
 LL | #![allow(non_exhaustive_omitted_patterns)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `non_exhaustive_omitted_patterns` lint is unstable
    = note: see issue #89554 <https://github.com/rust-lang/rust/issues/89554> for more information
@@ -22,10 +22,10 @@ LL | #![allow(non_exhaustive_omitted_patterns)]
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 warning: unknown lint: `non_exhaustive_omitted_patterns`
-  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:15:5
+  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:15:13
    |
 LL |     #[allow(non_exhaustive_omitted_patterns)]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `non_exhaustive_omitted_patterns` lint is unstable
    = note: see issue #89554 <https://github.com/rust-lang/rust/issues/89554> for more information
@@ -33,10 +33,10 @@ LL |     #[allow(non_exhaustive_omitted_patterns)]
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 warning: unknown lint: `non_exhaustive_omitted_patterns`
-  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:15:5
+  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:15:13
    |
 LL |     #[allow(non_exhaustive_omitted_patterns)]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `non_exhaustive_omitted_patterns` lint is unstable
    = note: see issue #89554 <https://github.com/rust-lang/rust/issues/89554> for more information
@@ -45,10 +45,10 @@ LL |     #[allow(non_exhaustive_omitted_patterns)]
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 warning: unknown lint: `non_exhaustive_omitted_patterns`
-  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:24:5
+  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:24:12
    |
 LL |     #[warn(non_exhaustive_omitted_patterns)]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `non_exhaustive_omitted_patterns` lint is unstable
    = note: see issue #89554 <https://github.com/rust-lang/rust/issues/89554> for more information
@@ -56,10 +56,10 @@ LL |     #[warn(non_exhaustive_omitted_patterns)]
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 warning: unknown lint: `non_exhaustive_omitted_patterns`
-  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:24:5
+  --> $DIR/feature-gate-non_exhaustive_omitted_patterns_lint.rs:24:12
    |
 LL |     #[warn(non_exhaustive_omitted_patterns)]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `non_exhaustive_omitted_patterns` lint is unstable
    = note: see issue #89554 <https://github.com/rust-lang/rust/issues/89554> for more information

tests/ui/feature-gates/feature-gate-strict_provenance_lints.stderr

@@ -1,8 +1,8 @@
 warning: unknown lint: `fuzzy_provenance_casts`
-  --> $DIR/feature-gate-strict_provenance_lints.rs:3:1
+  --> $DIR/feature-gate-strict_provenance_lints.rs:3:9
    |
 LL | #![deny(fuzzy_provenance_casts)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         ^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `fuzzy_provenance_casts` lint is unstable
    = note: see issue #130351 <https://github.com/rust-lang/rust/issues/130351> for more information
@@ -11,10 +11,10 @@ LL | #![deny(fuzzy_provenance_casts)]
    = note: `#[warn(unknown_lints)]` on by default
 
 warning: unknown lint: `lossy_provenance_casts`
-  --> $DIR/feature-gate-strict_provenance_lints.rs:5:1
+  --> $DIR/feature-gate-strict_provenance_lints.rs:5:9
    |
 LL | #![deny(lossy_provenance_casts)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         ^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `lossy_provenance_casts` lint is unstable
    = note: see issue #130351 <https://github.com/rust-lang/rust/issues/130351> for more information

tests/ui/feature-gates/feature-gate-test_unstable_lint.stderr

@@ -1,8 +1,8 @@
 warning: unknown lint: `test_unstable_lint`
-  --> $DIR/feature-gate-test_unstable_lint.rs:4:1
+  --> $DIR/feature-gate-test_unstable_lint.rs:4:10
    |
 LL | #![allow(test_unstable_lint)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |          ^^^^^^^^^^^^^^^^^^
    |
    = note: the `test_unstable_lint` lint is unstable
    = help: add `#![feature(test_unstable_lint)]` to the crate attributes to enable

tests/ui/feature-gates/feature-gate-unqualified-local-imports.stderr

@@ -1,8 +1,8 @@
 warning: unknown lint: `unqualified_local_imports`
-  --> $DIR/feature-gate-unqualified-local-imports.rs:3:1
+  --> $DIR/feature-gate-unqualified-local-imports.rs:3:10
    |
 LL | #![allow(unqualified_local_imports)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: the `unqualified_local_imports` lint is unstable
    = help: add `#![feature(unqualified_local_imports)]` to the crate attributes to enable

tests/ui/lint/must_not_suspend/gated.stderr

@@ -1,8 +1,8 @@
 warning: unknown lint: `must_not_suspend`
-  --> $DIR/gated.rs:4:1
+  --> $DIR/gated.rs:4:9
    |
 LL | #![deny(must_not_suspend)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         ^^^^^^^^^^^^^^^^
    |
    = note: the `must_not_suspend` lint is unstable
    = note: see issue #83310 <https://github.com/rust-lang/rust/issues/83310> for more information

tests/ui/unknown-unstable-lints/deny-unstable-lint-inline.stderr

@@ -1,8 +1,8 @@
 error: unknown lint: `test_unstable_lint`
-  --> $DIR/deny-unstable-lint-inline.rs:4:1
+  --> $DIR/deny-unstable-lint-inline.rs:4:10
    |
 LL | #![allow(test_unstable_lint)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |          ^^^^^^^^^^^^^^^^^^
    |
    = note: the `test_unstable_lint` lint is unstable
    = help: add `#![feature(test_unstable_lint)]` to the crate attributes to enable

tests/ui/unknown-unstable-lints/warn-unknown-unstable-lint-inline.stderr

@@ -1,8 +1,8 @@
 warning: unknown lint: `test_unstable_lint`
-  --> $DIR/warn-unknown-unstable-lint-inline.rs:4:1
+  --> $DIR/warn-unknown-unstable-lint-inline.rs:4:10
    |
 LL | #![allow(test_unstable_lint)]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |          ^^^^^^^^^^^^^^^^^^
    |
    = note: the `test_unstable_lint` lint is unstable
    = help: add `#![feature(test_unstable_lint)]` to the crate attributes to enable