[clang] [CIR] Build out AST consumer patterns to reach the entry point into CIRGen (PR #91007)

[Chuanqi Xu via cfe-commits]

https://github.com/ChuanqiXu9 commented:

BTW, it will be helpful to create subscribing team to help people to get informed in time. (I just saw the patch accidently.)

https://github.com/llvm/llvm-project/pull/91007