Integrate testing of maven semantic versioning

I have developed an experimental proof-of-concept for testing the behaviour of the semantic versioning in maven.gitlab-ci.yml, which currently is not fully complete/correct.

It could be helpful to further develop/improve these tests and integrate them into the pipeline for this repository.

Some possible approaches to consider here:

• The current testing approach used here relies on a branch of ci-templates which adds significant complexity to the script used in maven.gitlab-ci.yml. There could be an opportunity to spin out a separate executable for calculating the required version number which can be run in isolation, which would clean the script up and simplify the testing since it will no longer rely on yqing the maven.gitlab-ci.yml
• The tests are currently written as a bash script as that felt like the quickest way to PoC, since there was a lot of reliance on environment variables to the script. It could be beneficial to take the approach used here and migrate it (and possibily the standalone versioning executable above if appropriate) to Python