build_release_candidate.sh fails because of leftover RC tags in working git clone

Currently, the build_release_candidate.sh re-uses $HOME/build_release_candidate/beam as the git clone. If the RC tag already exists due to a prior build, it crashes. Instead, since that clone failed, it should just not be used the next time. The workflow that makes sense to me is:

- Locally tag the intended RC commit
- Try to build the RC from that
- If the RC build fails, remove tag / discard working branch / etc
- If the RC succeeds, push the tag (and if it is on a gradle release plugin commit, those commits)

Imported from Jira [BEAM-6598](https://issues.apache.org/jira/browse/BEAM-6598). Original Jira may contain additional context.
Reported by: kenn.
This issue has child subcomponents which were not migrated over. See the original Jira for more information.
Subtask of issue #19755