[llvm] [experimental] Ask copilot to check perf profile degradation (PR #146271)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

I'll land it, and if folks don't mind trying to ask copilot to review on various PRs they see - let's get a feel for its usefulness?

https://github.com/llvm/llvm-project/pull/146271