Enable bazel builds on `ciflow/default` (#62649)
Summary:
Add `regenerate.sh` convenience script
Remove "TODO: Reenable on PR" label from workflows which are enabled on PRs
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62649
Reviewed By: seemethere
Differential Revision: D30071905
Pulled By: malfet
fbshipit-source-id: c82134cb676b273d23e225be21166588996a31d3
