[llvm] [Github][CI] Add default gha user for tooling containers (PR #164294)

[Baranov Victor via llvm-commits]

vbvictor wrote:

> Shouldn't be difficult to push this to GHCR and run a test job with workflow modifications

Hmm, I didn't know I can push locally build images to GitHub. I'll check

https://github.com/llvm/llvm-project/pull/164294