DRILL-7706: Implement Drill RDBMS Metastore
1. Fix issue with undeterministic execution of batch update / delete statements, now they will be executed in the same order as they were added.
2. Abstracted Metastore common test classes to be used by different Metastore implementations.
3. Added drill-metastore-override-example.conf with example of Drill Metastore configuration.
4. Replaced list of metadata types which are required to be passed during read / write operations with set to avoid possible duplicates.
5. Add RDBMS Metastore implementation, README.md and unit tests.
