Rollup merge of #135171 - notriddle:notriddle/stable-path-is-better, r=GuillaumeGomez

rustdoc: use stable paths as preferred canonical paths

This accomplishes something like 16a4ad7d7b, but with the `rustc_allowed_through_unstable_modules` attribute instead of the path length.

Fixes #131676

tests/rustdoc/inline_local/fully-stable-path-is-better.rs

@@ -0,0 +1,40 @@
+//! Test case for [134702]
+//!
+//! [134702]: https://github.com/rust-lang/rust/issues/134702
+#![crate_name = "foo"]
+#![stable(since = "1.0", feature = "v1")]
+
+#![feature(staged_api, rustc_attrs)]
+
+#[stable(since = "1.0", feature = "stb1")]
+pub mod stb1 {
+    #[doc(inline)]
+    #[stable(since = "1.0", feature = "stb1")]
+    pub use crate::uns::Inside1;
+}
+
+#[unstable(feature = "uns", issue = "135003")]
+pub mod uns {
+    #[stable(since = "1.0", feature = "stb1")]
+    #[rustc_allowed_through_unstable_modules]
+    pub struct Inside1;
+    #[stable(since = "1.0", feature = "stb2")]
+    #[rustc_allowed_through_unstable_modules]
+    pub struct Inside2;
+}
+
+#[stable(since = "1.0", feature = "stb2")]
+pub mod stb2 {
+    #[doc(inline)]
+    #[stable(since = "1.0", feature = "stb2")]
+    pub use crate::uns::Inside2;
+}
+
+#[stable(since = "1.0", feature = "nested")]
+pub mod nested {
+    //! [Inside1] [Inside2]
+    //@ has foo/nested/index.html '//a[@href="../stb1/struct.Inside1.html"]' 'Inside1'
+    //@ has foo/nested/index.html '//a[@href="../stb2/struct.Inside2.html"]' 'Inside2'
+    use crate::stb1::Inside1;
+    use crate::stb2::Inside2;
+}