Keep latest metrics image tags updated and set commit image tags after kubectl apply

[damccorm]

Fixes two issues in :beam-test-infra-metrics:deploy:

• Tags and pushes :latest alongside :$CONTAINER_VERSION_NAME in build_and_publish_containers.sh so kubectl apply -f kubernetes/beamgrafana-deploy.yaml never pulls a stale :latest image.
• Runs kubectl set image after kubectl apply so the deployment records the explicit :${project.lastCommitId} tag rather than being overwritten by the untagged image in beamgrafana-deploy.yaml (and guards image.split(':') when no tag is present).