[clang] [Clang][AMDGPU] Add builtins for instrinsic `llvm.amdgcn.raw.buffer.store` (PR #94576)

[Krzysztof Drewniak via cfe-commits]

krzysz00 wrote:

`raw.ptr.buffer.load` (and `.store`) are loads and stores and should be able to deal with any type you could send through a normal pointer (especially since a partially-OOB read is already hardware-level UB, so extending that through the intrinsics is reasonable)

`struct.ptr.*` do have stronger legality constraints because of swizzling, but I'm not proposing we generalize those

https://github.com/llvm/llvm-project/pull/94576