[llvm] [Workflow] Add new code format helper. (PR #66684)

[Ingo Müller via llvm-commits]

ingomueller-net wrote:

My PR fails in this new CI target because `llvm/utils/git/requirements_formatting.txt` cannot be found. See output [here](https://github.com/llvm/llvm-project/actions/runs/6284641620/job/17066205762?pr=67241). I have rebased just now. Am I doing something wrong?

https://github.com/llvm/llvm-project/pull/66684