Dev Override for Kustomize (PROJQUAY-992)

[alecmerdler]

Issue: https://issues.redhat.com/browse/PROJQUAY-992

Changelog: Allow overriding Kustomize using a defined ConfigMap.

Docs: N/a

Testing:

1. Create ConfigMap called quay-dev-kustomize with the following contents in the kustomization.yaml key:

# Overlay variant for "dev".
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
commonAnnotations:
  quay-version: dev
bases:
  - ../../../tmp
images:
  - name: quay.io/projectquay/quay
    newName: quay.io/alecmerdler/quay
    newTag: dev

2. Install Quay Operator using custom CatalogSource.
3. Create QuayRegistry with spec.desiredVersion set to dev.

Operator should deploy Quay app container using the image override.

Details: By using Kustomize and having the static k8s files present in the Operator container, we lend ourselves to an escape hatch for overriding the deployed container images and other aspects of the QuayRegistry. This is done at the Operator level, so every QuayRegistry will be deployed using these overrides. Therefore this is for dev/debugging purposes and should not be used in production.