Rollup merge of #148769 - stabilize/alloc_layout_extra, r=scottmcm

Stabilize `alloc_layout_extra`

Tracking issue: rust-lang/rust#55724
FCP completed in rust-lang/rust#55724 (comment)
Closes rust-lang/rust#55724

----

As per rust-lang/rust#55724 (comment),
- `repeat_packed` and `extend_packed` are unchanged
- `repeat` now excludes trailing padding on the last element from the total array size
- `dangling` renamed to `dangling_ptr`
- `padding_needed_for` not stabilized, changed to accept `Alignment` instead of `usize` and moved to the `ptr_aligment_type` feature flag (tracking issue: rust-lang/rust#102070)

Author: jhpratt

patches/0027-sysroot_tests-128bit-atomic-operations.patch

@@ -14,11 +14,10 @@ diff --git a/coretests/tests/lib.rs b/coretests/tests/lib.rs
 index 1e336bf..35e6f54 100644
 --- a/coretests/tests/lib.rs
 +++ b/coretests/tests/lib.rs
-@@ -2,5 +2,4 @@
+@@ -2,4 +2,3 @@
  // tidy-alphabetical-start
 -#![cfg_attr(target_has_atomic = "128", feature(integer_atomics))]
  #![cfg_attr(test, feature(cfg_select))]
- #![feature(alloc_layout_extra)]
  #![feature(array_ptr_get)]
 diff --git a/coretests/tests/atomic.rs b/coretests/tests/atomic.rs
 index b735957..ea728b6 100644