delete obsolete files and shift webhook testing to use a kube-native approach

[grokspawn]

Description of the change:

1. identify obsolete artifacts in the repo that we can remove, thus reducing the problem domain some
2. shift e2e webhook testing to use the webhook-operator version which replaces the kube-rbac-proxy with kube api approaches
3. profit!

Motivation for the change:
gcr.io/kubebuilder/kube-rbac-proxy is gone, and there are still test bundles/images in OLM-land that rely on it.

Architectural changes:

Testing remarks:

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Bug fixes are accompanied by regression test(s)
• e2e tests and flake fixes are accompanied evidence of flake testing, e.g. executing the test 100(0) times
• tech debt/todo is accompanied by issue link(s) in comments in the surrounding code
• Tests are comprehensible, e.g. Ginkgo DSL is being used appropriately
• Docs updated or added to /doc
• Commit messages sensible and descriptive
• Tests marked as [FLAKE] are truly flaky and have an issue
• Code is properly formatted

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[tmshort]

/lgtm
The removed files are all in deploy/upstream/manifests

[rashmigottipati]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rashmigottipati, tmshort

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