This is done by checking for existing issues only in the milestone
corresponding to the current branch. For issues, the milestone is assigned
at the time of issue creation. For PRs, since the branch is different the
milestone can be derived from that while triaging the issue.
Closes gh-20680
Update CI scripts so that command failures do not cause an immediate
exit. Prior to this commit, some of our looping logic would never run
because the entire script would exit.