[clang] [CIR] Support packed boolean vectors (ext_vector_type of bool) (PR #215653)

[Amr Hesham via cfe-commits]

AmrDeveloper wrote:

Is it fixing the same issue as #212146 but with a different approach (on the CIR CG level, not during lowering), because I can run the same tests (Except the case of a vec of 4; I was planning to add `emitBoolVecConversion` support as a follow-up 🤔 

https://github.com/llvm/llvm-project/pull/215653