Rollup merge of #93613 - crlf0710:rename_to_async_iter, r=yaahc

Move `{core,std}::stream::Stream` to `{core,std}::async_iter::AsyncIterator`

Following amendments in https://github.com/rust-lang/rfcs/pull/3208/.

cc #79024
cc ``@yoshuawuyts`` ``@joshtriplett``

library/alloc/src/lib.rs

@@ -91,7 +91,7 @@
 #![feature(array_chunks)]
 #![feature(array_methods)]
 #![feature(array_windows)]
-#![feature(async_stream)]
+#![feature(async_iterator)]
 #![feature(coerce_unsized)]
 #![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
 #![feature(const_box)]