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

[Matin Raayai via llvm-commits]

matinraayai wrote:

@arsenm @aeubanks this should be good to merge. Please merge it ASAP to prevent any more surprise new uses of TM in master that require migrating.

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