[CI] Fix additional CI jobs not launched when PR is created from fork repo (#47969)
Summary:
`CIRCLE_PR_NUMBER` is not always set during CI.
This is to extract PR NUMBER from BRANCH info in order to launch additional CI jobs.
Should allow tag:`ci/binaries` and `ci/all` worked on forked PRs
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47969
Reviewed By: janeyx99
Differential Revision: D24991790
Pulled By: walterddr
fbshipit-source-id: 3ca30752135d54236a9abf0610eb89946852d45a
