Run MPS tests (#78723)
This adds a workflow, that is executed on MacOS 12.3+ machines and runs just test_mps.py
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78723
Approved by: https://github.com/albanD, https://github.com/kulinseth
(cherry picked from commit f7ac389e71e55f84651141c01334dea668b3f90c)
