Rollup merge of #94635 - jhpratt:merge-deprecated-attrs, r=davidtwco

Merge `#[deprecated]` and `#[rustc_deprecated]`

The first commit makes "reason" an alias for "note" in `#[rustc_deprecated]`, while still prohibiting it in `#[deprecated]`.

The second commit changes "suggestion" to not just be a feature of `#[rustc_deprecated]`. This is placed behind the new `deprecated_suggestion` feature. This needs a tracking issue; let me know if this PR will be approved and I can create one.

The third commit is what permits `#[deprecated]` to be used when `#![feature(staged_api)]` is enabled. This isn't yet used in stdlib (only tests), as it would require duplicating all deprecation attributes until a bootstrap occurs. I intend to submit a follow-up PR that replaces all uses and removes the remaining `#[rustc_deprecated]` code after the next bootstrap.

`@rustbot` label +T-libs-api +C-feature-request +A-attributes +S-waiting-on-review

compiler/rustc_passes/src/stability.rs

@@ -202,7 +202,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
                     self.tcx.sess,
                     *span,
                     E0549,
-                    "rustc_deprecated attribute must be paired with \
+                    "deprecated attribute must be paired with \
                     either stable or unstable attribute"
                 )
                 .emit();