[llvm] Reapply "[CodeGen][AArch64] Avoid duplicate hints in register allocation (#219007)" (#224451) (PR #224742)

[Tomer Shafir via llvm-commits]

https://github.com/tomershafir commented:

I agree that given the regression test is more complex to implement it may not worth it, while the unit test provides direct coverage that is effectively inclusive.

I made a small comment about the patch structure

https://github.com/llvm/llvm-project/pull/224742