[llvm] [workflows] Port buildkite Windows config to GitHub actions (PR #82093)

[Tom Stellard via llvm-commits]

tstellar wrote:

I believe I've addressed all the review comments now.  I'm not sure what the current status is on Buildkite and if there are still issues with long queue times, but this job is ready to be used as a drop-in replacement if needed.

https://github.com/llvm/llvm-project/pull/82093