Add v1beta2 e2e test coverage

[anmazzotti]

The e2e tests should be expanded with v1beta2 resources.
The current tests can absolutely stay to test conversion, but they should be ported to v1beta2 in parallel.

Probably a good occasion to cover the CustomDefaulter for KThreesConfig and KThreesControlPlane resources as well.

[nasusoba]

I have drafted a PR for using v1beta2 #124 , we also need to test clusterclass, we could also track clusterclass e2e testing here!

[nasusoba]

I added an upgrade test for clusterclass in the drafted PR, but it seems that it does not trigger rollout, and the version for the machines remain old version. May need to do some investigation.

[nasusoba]

The .Status.Version field is missing, results in rollout not triggered, fixed in #127 . Also MachinePools related test is not working, will disable them first. The upgrade could be successfully run after the fix.