Enhance the clickstream ksqlDB demo to create connectors using ksqlDB

You can now create connectors _within_ ksqlDB. We're already using `SOURCE` connectors within the demo. We should update the demo to:

* Not run connect as a separate container, but run within ksqlDB
* Use the `CREATE SINK CONNECTOR` syntax in ksqlDB to create the connectors to sink to ES, and remove `ksql-connect-es-grafana.sh`.

The whole _create source connectors_, _execute sql statements_, _create sink connectors_, could be in a single SQL script....