Enable manual test config label selection on GHA macos (#84895)
Following up with https://github.com/pytorch/pytorch/pull/83690 and https://github.com/pytorch/pytorch/pull/84669, functorch team has started using the new label in some of their [PRs](https://github.com/pytorch/pytorch/labels/test-config%2Ffunctorch). This is to enable manual test config using label on GHA macos.
This also works with `ciflow/mps` as follows:
* If only `test-config/functorch` is present, no arm64 build is performed and mps test is skipped
* If only `ciflow/mps` is present, mps test is run in addition to all other tests
* If both `test-config/functorch` and `ciflow/mps` is present, both functorch and mps tests are run
* If none of the label is present, pull workflow is run as usual
### Issues
#82367
Pull Request resolved: https://github.com/pytorch/pytorch/pull/84895
Approved by: https://github.com/ZainRizvi
