[llvm] [X86] Reimplement bundle alignment mode (PR #175830)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay requested changes to this pull request.

You can apply some simplifications here https://github.com/MaskRay/llvm-project/tree/bundle-align

https://github.com/llvm/llvm-project/pull/175830