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

[Krzysztof Drewniak via cfe-commits]

krzysz00 wrote:

Re addrspace 7, there's one major piece of work missing: arbitrary-typed inputs.
That is, we can't currently handle, for example, `load <16 x i8>, ptr addrspace(7) %p` (or, worse, `load i256, ptr addrspace(7) %p`.
That's been a followup ticket I never have time to do.

If we do want addrspace(7), we'll need to expose `make.buffer.rsrc` and give it a `p7` variant probably.

And even so, we'll want addrspace(8) to work because there are non-raw buffers (ex. swizzling).

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