Productize new container crw-dashboard-rhel8

Onboard dashboard image like we did for DWO and DWCO in CRW-1671.

Currently, it's apache-based (the same as registries) https://github.com/eclipse/che-dashboard/blob/master/apache.Dockerfile but later we will move it to node server (like theia).

From CRW operator stuff, it's the same as other related images https://github.com/eclipse-che/che-operator/pull/684/files#diff-1d312bcc873ef43c50cf404911da0e77a1d74f999ef83e63cd6ca8eeb42dfe93R53

Requirements:

• new comet build entry ==> pkgs.devel repo
• new comet dellivery entry ==> RHEC url (make sure added to the correct errata targets/branches)
• new folder in crw-images repo to contain sources transformed/synced from upstream
• new sync.sh script to handle sync logic
• new get-sources.sh script to handle fetching any third party deps not able to be synced (or vendored) directly in the source tree
• include container in scripts getLatestImageTags.sh, tagRelease.sh, and manifest/get-3rd-party-deps-manifests.sh
• implement Jenkins job to build in 2.9 and 2.x branches
• create image in quay https://quay.io/repository/crw/dashboard-rhel8 and set correct owners/creators permissions so humans and bots can push content
• add to build-all-images job so it can be rebuilt weekly
• update deploy/operator.yaml in 2.9 and 2.x branches (see codeready-workspaces-operator/build/scripts/sync*.sh) to replace this:

              - name: RELATED_IMAGE_dashboard
                value: quay.io/eclipse/che-dashboard:next
  

  with

              - name: RELATED_IMAGE_dashboard
                value: registry.redhat.io/codeready-workspaces/dashboard-rhel8:2.9