Additional fixes
- upgrade ubuntu-test.docker to ubuntu 22.04 (and some small fixes brought forward from CASSANDRA-20997)
- (.jenkins/k8s) changes gke's small node pool from n2-highcpu-8 to e2-highcpu-8 (gke's own pod resources reqs increased)
- (.jenkins/k8s) limit one agent pod per node (when jenkins is deployed in k8s using our helm)
- (.jenkins/k8s) add the cassandra-6.0 job
- pass maven.repo.local sys prop, if set, into accord's gradle build
- check and fail on maven dependencies checksums when downloading
- when on-the-fly building docker images add `--load` (podman compatbility)
- newer python versions can use venv instead of virtualenv
- rename ubuntu2004_test.docker to ubuntu-test.docker (in 5.0)
- (Jenkinsfile) fix retries (which was no longer working when agents/nodes died, since CASSANDRA-20833)
- (Jenkinsfile) @NonCPS where (now) needed
- (Jenkinsfile) fix default value for the branch parameter (after a new helm deploy)
- (.build/run-ci) fix missing parameters on jobs also at helm deploy time
- (.build/run-ci) .git suffixes on repo urls are optional
patch by Mick Semb Wever; reviewed by Dmitry Konstantinov, Stefan Miklosovic for CASSANDRA-21403
mck