Add tests for version comparison helpers

Summary

Adds tests for version comparison helpers to investigate failures described in #973 (closed).

I've noticed that despite all upgrade steps being completed, the Reconcile loop continually repeats stating upgrade: true. By that point, the Operator should have updated the Status version of the CR with the new version so that this doesn't happen. I have a feeling it's failing to update that field, which causes the reconcile loop to repeat far longer than it should

Testing

TEST_PKGS="./pkg/gitlab/internal/v1beta1/..." task unit-tests