Rollup merge of #49400 - Diggsey:shrink-to, r=joshtriplett

Implement `shrink_to` method on collections

Fixes #49385

src/libstd/lib.rs

@@ -298,6 +298,7 @@
 #![feature(raw)]
 #![feature(rustc_attrs)]
 #![feature(stdsimd)]
+#![feature(shrink_to)]
 #![feature(slice_bytes)]
 #![feature(slice_concat_ext)]
 #![feature(slice_internals)]