test/e2e: Incluster test suite

[sunjayBhatia]

Now that the e2e tests no longer run Contour in a k8s cluster, we have actually lost a bit of coverage. We need to add an in-cluster test suite to make sure that Contour and our example deployment work actually in a cluster.

This suite should be focused on validating features of Contour and/or the example deployment that are only coverable in an actual k8s cluster, e.g. validating RBAC

• [x] Initial suite setup: https://github.com/projectcontour/contour/pull/4170
• [ ] RBAC for all relevant resources should be covered (partially covered in above, need to add more for Gateway API rbac etc.)
• [ ] Coverage over the various fields in the Contour manifest (e.g. update strategies in envoy/contour deployments)