[CI] Add known ciflow labels to probot (#94368)
Add `collect_ciflow_labels.py` that automatically extracts all labels from workflow files and adds the to pytorch-probot.yml
Same script can also be used to validate that all tags are referenced in the config
Add this validation to quickchecks
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94368
Approved by: https://github.com/jeanschmidt
