[clang] [CIR][ARM] Add base 32-bit ARM (GenericARM) codegen and lowering (PR #204360)

[Akshay K via cfe-commits]

kumarak wrote:

> @kumarak If you can rebase this PR now that the pointer-size support has been merged, I'll take another look. It looks like your other CIR changes are dependent on this one.

@andykaylor, I rebased this PR with main and also updated descriptions. This is the base support for 32-bit ARM codegen and lowering. Calling conventions (like AAPCS), arm-specific attributes, lowering, etc., are not supported yet. I will look into them as follow-up PRs

https://github.com/llvm/llvm-project/pull/204360