[clang] [clang] Introduce `SemaCoroutine` (PR #92645)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

While I am not against the idea about splitting Sema, the implementation detail makes me slightly concerning. What I had in mind is to split `SemaC`, `SemaCXX` (this can be derived class of `SemaCXX`), `SemaObjC` and other dialects (e.g., ACC or CUDA) out of `Sema`. Then big features of C++ can be member of `SemaCXX` as `SemaCoroutine`, `SemaConcept`...

https://github.com/llvm/llvm-project/pull/92645