Improve argument parsing of promote-nightly-to-release

[fredemmott]

Currently, skipping a release requires manually editing this script to change MINOR-1 to MINOR-2, and suppressing the various checks in it.

• fully support this case with --previous
• add --force to permit local changes
• add --dry-run to verify inferred version
• improve argument parsing significantly
• move the workdir check before the git check, as the git check fails if the workdir is wrong

Options (including --help) can come before or after the arguments, as long as -- isn't specified.

Test plan:

• Used to tag and start build of 4.133 (with --previous=4.131)
• ran without --previous and with --dry-run to verify the MINOR-1 logic still works
• needed --force to run as I hadn't committed this yet.

[fredemmott]

I'm going to follow up by adding a github action that runs shellcheck

[fredemmott]

I'm going to follow up by adding a github action that runs shellcheck

Done in #256