[llvm] [CodeGen] Port AtomicExpand to new Pass Manager (PR #71220)

[Rishabh Bali via llvm-commits]

Ris-Bali wrote:

> > > > Should I revert the formatting changes in `llvm/include/llvm/CodeGen/Passes.h` ? most of the formatting changes done are not related to this PR but were still being detected by `check_code_formatter` so I had to comply.
> > > 
> > > 
> > > Sorry for the unclear request, just use `git clang-format` to format the original patch.
> > 
> > 
> > The problem is the formatting tests only passes if Passes.h is fully formatted([prev_commit](https://github.com/llvm/llvm-project/pull/71220/commits/02b535096e47c1f7f00acd31dee507adf268a89c)) (the tests fail with the latest commit where I reverted the formatting changes" originally I have changed a single line in that file. git clang-format is currently formatting the entire file. It may be a bug although I am not sure
> 
> You can squash the change here.

Have squashed the changes.

https://github.com/llvm/llvm-project/pull/71220