[Cloud Deploy] Bare minimum to create a Cloud Deploy pipeline to release Website and mixer

[gmechali]

Part 1.b of setting up a new CloudDeploy Pipeline(s) for DataCommons.
For now, we will setup 2 CloudDeploy pipelines, one for the Mixer deployments, and one for Website + its mixer.

The changes in this PR modify the website side of the deployment and works in conjunction with the changes in https://github.com/datacommonsorg/mixer/pull/5350.

You can see the new CloudDeploy Pipelines here: https://pantheon.corp.google.com/deploy/delivery-pipelines?e=13803378&inv=1&invt=Ab4Qog&mods=-monitoring_api_staging&project=datcom-ci

You can trigger an external mixer release with the following command:

MIXER_HASH=e9523a5
TIMESTAMP=$(date +"%Y%m%d-%H%M%S")
gcloud deploy releases create "gmechali-manual-$TIMESTAMP" \
--delivery-pipeline=datacommons-mixer-release-pipeline \
--region=us-central1 \
--skaffold-file=skaffold.yaml \
--images="[gcr.io/datcom-ci/datacommons-mixer=us-docker.pkg.dev/datcom-ci/gcr.io/datacommons-mixer:$MIXER_HASH](http://gcr.io/datcom-ci/datacommons-mixer=us-docker.pkg.dev/datcom-ci/gcr.io/datacommons-mixer:$MIXER_HASH)" \
--deploy-parameters="mixer.githash=$MIXER_HASH" \
--project=datcom-ci

[dwnoble]

Where does "Release.Namespace" get populated from?