Change the release process to automate the changelog

[Judit Knoll]

Currently the trigger of the release process is a tag push on master branch of spotbugs/spotbugs (and for having the master changes for the eclipse update site, a simple commit push). When a GitHub Action is running on a tag push, it's not in a branch, but in detached head state, so no commit can be pushed to that branch.
If we would like to automate the changelog creation and update the CHANGELOG.md file, I see two options (please let me know, if you see other options):

1. change the trigger of the release process, let the release process update the changelog file,
   • IMO would be really nice, if the changelog modifying commit would be included in the release, so the the tag would be either in this commit or after it,
2. create a separate GitHub action just for updating the changelog file,
   • this needs to be separately triggered as part of the release process.

Release procedure documentation: RELEASE_PROCEDURE.md.
Release process github action: release.yml.
Connecting issue: #2921

[Andrey Loskutov]

I believe first option sounds better, but I'm fine with any option, do whatever you prefer.