[clang] [CIR][ARM] Generic 32-bit ARM codegen and lowering support (PR #204360)

[Akshay K via cfe-commits]

kumarak wrote:

Thanks, @andykaylor and @banach-space, for your feedback. 

As suggested, I split the PR into two separate PRs: `this-return` ABI support (https://github.com/llvm/llvm-project/pull/204185) and `array-cookie` handling (https://github.com/llvm/llvm-project/pull/206827). Please let me know your thoughts. 

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