[llvm] [WIP][Github][CI] Add separate container for code-format premerge job (PR #161083)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 commented:

I don't think this is the right approach.
1. Building LLVM yet another time for another container doesn't make much sense. We should probably be building this as an offshoot of the PGO optimized container so we can keep all the builds together. That complicates version updates though.
2. The number of container build workflows that have basically the exact same contents are getting high. It needs to get refactored into a common action that can be invoked with a dockerfile path/image name.

https://github.com/llvm/llvm-project/pull/161083