Automated bugfix release

@Cadair suggested that maybe we can use https://docs.github.com/en/actions/deployment/targeting-different-environments/using-environments-for-deployment to fully automated bugfix releases. For instance, maybe a GitHub comment to trigger bot PR to render towncrier change log, and another comment to push to PyPI, and so on.

cc @astropy/core-release-maintainers

Start with the linked GitHub Actions environments documentation and the discussion about comment-triggered bot pull requests, towncrier changelog rendering, and PyPI publishing. No file, test, or existing workflow entry point is named; done would require defining and implementing the automated bugfix release flow.

Written by the indexing model from the issue text.