Rollup merge of rust-lang#79213 - yoshuawuyts:stabilize-slice-fill, r=m-ou-se

Stabilize `core::slice::fill`

Tracking issue rust-lang#70758

Stabilizes the `core::slice::fill` API in Rust 1.50, adding a `memset` doc alias so people coming from C/C++ looking for this operation can find it in the docs. This API hasn't seen any changes since we changed the signature in rust-lang#71165, and it seems like the right time to propose stabilization. Thanks!

r? `@m-ou-se`

Author: Dylan-DPC

library/core/src/slice/mod.rs

@@ -2581,14 +2581,12 @@ impl<T> [T] {
     /// # Examples
     ///
     /// ```
-    /// #![feature(slice_fill)]
-    ///
     /// let mut buf = vec![0; 10];
     /// buf.fill(1);
     /// assert_eq!(buf, vec![1; 10]);
     /// ```
     #[doc(alias = "memset")]
-    #[unstable(feature = "slice_fill", issue = "70758")]
+    #[stable(feature = "slice_fill", since = "1.50.0")]
     pub fn fill(&mut self, value: T)
     where
         T: Clone,