[clang] [llvm] [X86] Replace X86 specific PDEP/PEXT handling with generic intrinsics (PR #204144)

[Jan Schultke via cfe-commits]

eisenwave wrote:

On the note of C++, https://github.com/cplusplus/papers/issues/2279 has been forwarded to LWG for inclusion in C++29, but we're still busy designing the `std::wide_result` return type, so it didn't go into the draft yet.

There also seems to be mild interest in having `clmul` in WebAssembly:
- https://github.com/WebAssembly/design/issues/1388

https://github.com/llvm/llvm-project/pull/204144