Add mac-mps workflow (#83296)
Which invokes only MPS tests if `ciflow/mps` tag is added
Use `sync-tag` to make jobs in those workflows dependent
Tested that it triggers the workflow if tag is added, see https://github.com/pytorch/pytorch/actions/runs/2843088226
Pull Request resolved: https://github.com/pytorch/pytorch/pull/83296
Approved by: https://github.com/huydhn, https://github.com/seemethere
