Automate Kubernetes cluster QA tests

Created by: slimsag

Today our release process https://github.com/sourcegraph/sourcegraph/issues/13374 indicates you should create a Kubernetes cluster, deploy Sourcegraph on it, run the e2e test initializer on it, and run the regression test suite on it:

• New Sourcegraph Kubernetes cluster:
  • Run the initializer on a new Sourcegraph Kubernetes cluster.
  • Run the regression test suite.

There has to be a better way we can reduce the number of manual steps here, maybe using Pulumni or some other form of scripting for this. Let's investigate and find possible opportunities, even if we don't get around to actually implementing them in 3.21.