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

[Tom Stellard via llvm-commits]

tstellar wrote:

I ran this job with `-DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;flang;lld;llvm;mlir;polly" ` which matches what buildkite does when there is a change made to llvm and just the build took 5h and 59m, so there was no time left to run the tests (GitHub timeout is 6 hours).  I'm going to try to do some benchmarks with the other combinations of projects.

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