Cleanup end-to-end test poms

The poms for the various end-to-end modules require some attention.

We can streamline the shade-plugin configuration by moving common elements to the parent pom.

Most modules explicitly depend on flink-core; in the spirit of being similar to quickstart projects (i.e. the template for user-jars) we should remove this dependency. It is transitively pulled in by the API modules flink-java and flink-streaming-java.

Other problems:

• several flink dependencies are not set to provided
• the datastream-allround-test has a hard-coded scala version in it's rocksdb dependency.
• The ttl test depends on rocksdb but doesn't actually use it