Rollup merge of #116839 - joboet:xous_thread_parking, r=m-ou-se

Implement thread parking for xous

This follows the pattern set by [the Windows parker](ddef56d5df/library/std/src/sys/windows/thread_parking.rs) when it uses keyed events. An atomic variable is used to track the state and optimize the fast path, while notifications are send via the ticktime server to block and unblock the thread.

ping `@xobs`
`@rustbot` label +T-libs +A-atomic
r? libs

library/std/src/lib.rs

@@ -336,6 +336,7 @@
 #![feature(portable_simd)]
 #![feature(prelude_2024)]
 #![feature(ptr_as_uninit)]
+#![feature(ptr_from_ref)]
 #![feature(raw_os_nonzero)]
 #![feature(round_ties_even)]
 #![feature(slice_internals)]