Made improvements to isGreen (#79619)
Relates to #76700
**Overview**: Made regex a local variable in the `isGreen` method and improved debugging message for missing relevant workflows. If there are required workflows missing, the message will now print which workflows were not found.
**Test Plan**: Updated relevant test case in `test_print_latest_commits.py`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79619
Approved by: https://github.com/janeyx99
