[llvm] Overhaul the TargetMachine and LLVMTargetMachine Classes (PR #111234)

[Matin Raayai via llvm-commits]

matinraayai wrote:

@aeubanks @arsenm it's been 3 weeks and I haven't gotten any comments regarding the interface rework. How do you want to proceed?

https://github.com/llvm/llvm-project/pull/111234