[clang] [CIR] Parse .cir cc1 input and support -emit-cir from it (PR #228288)

[Konstantinos Parasyris via cfe-commits]

koparasy wrote:

@bcardosolopes, @erichkeane , @andykaylor I would love to get some feedback on this one. I measured binary size, and the size increase is in the order of 60KB on my build. 

https://github.com/llvm/llvm-project/pull/228288