Add v1beta2 and clusterclass test for e2e

[nasusoba]

• Use kustomize to generate templates, so that we won't need to duplicate the change for each templates
• Test specs
  • Use v1beta2 template as a default template
  • Add a create test for v1beta1 for testing conversion
  • Add two tests (create + upgrade) for clusterclass
• Maintainance: Upgrade test framework to use 1.7.x CAPI core and CAPD
• Note: Capi's clusterclass test included machinepool, so I also include it in the templates, but MachinePools related functionality for our controllers is not ready, will be tracked in Support MachinePools #126 .

#123