Rollup merge of #92632 - yoshuawuyts:stabilize-available-parallelism, r=joshtriplett

Implement stabilization of `#[feature(available_parallelism)]`

Stabilized in #74479 (comment). Closes #74479. Thanks!

cc/ ``@rust-lang/libs-api``

Author: ehuss

library/std/src/thread/mod.rs

@@ -1504,7 +1504,6 @@ fn _assert_sync_and_send() {
 ///
 /// ```
 /// # #![allow(dead_code)]
-/// #![feature(available_parallelism)]
 /// use std::{io, thread};
 ///
 /// fn main() -> io::Result<()> {
@@ -1516,7 +1515,7 @@ fn _assert_sync_and_send() {
 #[doc(alias = "available_concurrency")] // Alias for a previous name we gave this API on unstable.
 #[doc(alias = "hardware_concurrency")] // Alias for C++ `std::thread::hardware_concurrency`.
 #[doc(alias = "num_cpus")] // Alias for a popular ecosystem crate which provides similar functionality.
-#[unstable(feature = "available_parallelism", issue = "74479")]
+#[stable(feature = "available_parallelism", since = "1.59.0")]
 pub fn available_parallelism() -> io::Result<NonZeroUsize> {
     imp::available_parallelism()
 }

library/test/src/lib.rs

@@ -16,7 +16,6 @@
 #![unstable(feature = "test", issue = "50297")]
 #![doc(test(attr(deny(warnings))))]
 #![feature(nll)]
-#![feature(available_parallelism)]
 #![feature(bench_black_box)]
 #![feature(internal_output_capture)]
 #![feature(staged_api)]