(CDAP-559) Remove usage of CombinedClassLoader in ProgramClassLoader

- Also code cleanup around FilterClassLoader and ApiResourceListHolder
- Remove unneeded classes from MR and Spark job to make job starts faster.
- disable chatty logging from beanutils during test
The `ServiceWorkerTwillRunnable` is defined in app-fabric, not in api, hence need special handling. Going though the Class.forName will give ClassNotFoundException (which is correct). In the old code, since we have the Class leaking bug, it works, but wrong.