[clang] [llvm] [clang] Introduce target-specific `Sema` components (PR #93179)

[Vlad Serebrennikov via llvm-commits]

Endilll wrote:

> Mildly curious that there isn't a SemaX86?
> 
> Doh, there already is one. Don't mind me.

This PR was based on the success with X86 and RISCV.

https://github.com/llvm/llvm-project/pull/93179