Update deprecated gradle setups and remove unsupported Python 2.x test

[kdebisschop]

Other pull requests are failing because Python 2.x is no longer natively supported on GitHub with Ubuntu-latest.

Also, the gradle test step is headed for trouble due to several deprecations:

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, actions/setup-java@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default

The set-output command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

This patch removes the Python 2.x build. Github no longer supports and 2.x version of python, we would need to build our own docker image or use a contributed image of potentially unknown quality to retain that testing.

This patch also upgrades the setup-checkout and setup-java to the current versions. This requires choosing a Java version. I had no real basis for what I should choose, I used corretto...but not for any particular reason.

The gradle/java changes also apply to releasing, and have been added there.