VMC Cleanup Tracking Issue

[chrischdi]

We're in the process of setting up community owned infra for CI.

After completion we should cleanup everything related to the old VMC environment.

• hack/e2e.sh : if's for toggling options
• hack/tools/janitor/main.go : flags
• hack/clean-ci.sh : if for JANITOR_ARGS
• test/e2e/config/config-overrides-mirror-prow.yaml: delete
• Makefile : parts of generate-test-infra-prowjobs target
• ...