Automate Cassandra/DSE version upgrades

[emerkle826]

When new versions of Cassandra or DSE are released, we have to manually edit files to pick them up. These include:

• Updating the version Matrix in the README.md
• Updating the version in the Dockerfiles
• Updating the version in the agent pom.xml files
• Updating the version lists in the docker-release GitHub action

As well as a changelog entry. For an example of some of the changes, see #452

It would be nice to have a script that creates a PR with all of these changes generated automatically for a give Cassandra/DSE version update.

- [ ] When a new version of Cassandra or DSE is introduced, a script can be run to make all the appropriate changes above
- [ ] BONUS: The script also pushes the changes and generates a PR that is ready to merge if the tests pass.

┆Issue is synchronized with this Jira Story by Unito
┆Issue Number: MAPI-8