Move user / schema creation to OARS

Some cleanup work here:

Renaming "clickhouse_service" to just "clickhouse" to match other services
Making the exposed ports match the base service as we do in other services
Moving cross-service users / database creation to the OARS plugin (https://github.com/openedx/tutor-contrib-oars/pull/8)

openedx-unsupported / tutor-contrib-clickhouse