[llvm] [GitHub][CI] Add clang-tidy premerge workflow (PR #154829)

[Baranov Victor via llvm-commits]

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+PyGithub==1.59.1
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vbvictor wrote:

It can, but we will install `black` and `darker` for each run. It's not a big deal performance-wise I guess.

https://github.com/llvm/llvm-project/pull/154829