Auto merge of #95960 - jhpratt:remove-rustc_deprecated, r=compiler-errors

Remove `#[rustc_deprecated]`

This removes `#[rustc_deprecated]` and introduces diagnostics to help users to the right direction (that being `#[deprecated]`). All uses of `#[rustc_deprecated]` have been converted. CI is expected to fail initially; this requires #95958, which includes converting `stdarch`.

I plan on following up in a short while (maybe a bootstrap cycle?) removing the diagnostics, as they're only intended to be short-term.

Author: bors

alloc/src/slice.rs

@@ -657,7 +657,7 @@ impl<T> [T] {
     /// ```
     #[rustc_allow_incoherent_impl]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_deprecated(since = "1.3.0", reason = "renamed to join")]
+    #[deprecated(since = "1.3.0", note = "renamed to join")]
     pub fn connect<Separator>(&self, sep: Separator) -> <Self as Join<Separator>>::Output
     where
         Self: Join<Separator>,

core/src/alloc/layout.rs

@@ -419,9 +419,9 @@ impl Layout {
 }
 
 #[stable(feature = "alloc_layout", since = "1.28.0")]
-#[rustc_deprecated(
+#[deprecated(
     since = "1.52.0",
-    reason = "Name does not follow std convention, use LayoutError",
+    note = "Name does not follow std convention, use LayoutError",
     suggestion = "LayoutError"
 )]
 pub type LayoutErr = LayoutError;