This adds support for automatically cherry-picking and testing fixes for the
release branch using 'commands' in issue comments. The two supported commands are:
/cherry-pick <commit1> <commit2> ...
Which will backport and test commits from main. And also
/branch owner/repo/branch
Which will test commits from the given branch.
Reviewed By: alexbatashev, kwk
Differential Revision: https://reviews.llvm.org/D117386
Also, replace the existing actionscript implementation with a python
script that can be run outside of GitHub Actions. The intention is
that going forward, all github action functionality would be implemented
in this script.
Reviewed By: kwk
Differential Revision: https://reviews.llvm.org/D116762