DRILL-2826: Simplify and centralize Operator Cleanup
- Remove cleanup method from RecordBatch interface
- Make OperatorContext creation and closing the management of FragmentContext
- Make OperatorContext an abstract class and the impl only available to FragmentContext
- Make RecordBatch closing the responsibility of the RootExec
- Make all closes be suppresing closes to maximize memory release in failure
- Add new CloseableRecordBatch interface used by RootExec
- Make RootExec AutoCloseable
- Update RecordBatchCreator to return CloseableRecordBatches so that RootExec can maintain list
- Generate list of operators through change in ImplCreator
