gdss-brick >> gh17 - Redesign disk storage:

Summary:
- Add rename ops DB to record rename/6 operations performed while
  the Scavenger is running. (WIP)

Details:
- gmt_hlog:
  * Add create_rename_op_db/1, get_rename_op_db/1 and delete_rename_
    op_db/1.
- gmt_hlog_common:
  * Add a field 'should_record_rename_ops' to the state record.
  * Refactor write_back_to_stable_storage1/4 and extracted a new
    function write_back_to_metadata_db/4.
  * Add record_rename_ops/4 and relevant functions.