Deploying registries in OpenShift - All templates for deployment must be reworked

The openshift deployment template for the CRW plugin registry has Che defaults in it.

That file is in fact COPIED to downstream here: http://pkgs.devel.redhat.com/cgit/containers/codeready-workspaces-pluginregistry/tree/openshift/che-plugin-registry.yml?h=crw-2.6-rhel-8#n103

But it's not YET in the midstream repos:

• https://github.com/redhat-developer/codeready-workspaces/tree/crw-2.5-rhel-8/dependencies/che-devfile-registry
• https://github.com/redhat-developer/codeready-workspaces-images (coming in 2021 in CRW-1275)

Bigger issue is that the version included in CRW sources in pkgs.devel is not transformed to include CRW defaults; it still has Che defaults:

parameters:
- name: IMAGE
  value: quay.io/eclipse/che-plugin-registry
  displayName: Eclipse Che plugin registry image
  description: Che plugin registry Docker image. Defaults to eclipse/che-plugin-registry
- name: IMAGE_TAG
  value: nightly
  displayName: Eclipse Che plugin registry version
  description: Eclipse Che plugin registry version which defaults to nightly

So at minimum we need to transform those lines. Perhaps more, not sure. abazko would need to provide input here.

Telling people to use that file is going to be error-prone, until we get it properly downstreamed, get it into a public-facing repo (CRW-1275) to which we can refer from the docs, and get it updated to include the correct CRW defaults. 

Also there's no downstreamed devfile deployment registry, so that one needs to be downstreamed before we can refer to it.

GoogleDoc for drafting:
https://docs.google.com/document/d/1SnG_GRAC9F0fElwZ0_5JVBfXzQJeFpkwNcU2ZessV9k/edit