[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 test only passes if Passes.h is fully formatted (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

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