[clang] [clang] Implement `__is_layout_compatible` (PR #81506)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

Thank you for this! Please be sure to also add a release note and documentation (https://clang.llvm.org/docs/LanguageExtensions.html#type-trait-primitives).

https://github.com/llvm/llvm-project/pull/81506