Renovate should monitor postgres and big-bang/base images

In renovate, only the sonarqube image is currently being monitored. It should also monitor the images in chart/templates/deployment.yaml, chart/deps/postgresql/values.yaml and tests/test-values.yaml for updates. Specifically, the postgres image in deployment.yaml, postgresql, minideb, and postgres-exporter in the dependencies, and the big-bang/base image in test-values.yaml. These are test resources only, but should be kept up to date by the code owners.

The ones in the deps folder could be caught by the default renovate if the ignore path is changed