In version 0.13, we support a more efficient compaction logic.
This logic will maintain multiple version paths of the tablet.
This can avoid -230 errors and can also support incremental clone.
But the previous incremental clone uses the incremental rowset meta recorded in `incr_rs_meta`.
At present, the incremental rowset meta recorded in `incr_rs_meta` and the records
in `stale_rs_meta` are duplicated, and the current clone logic does not adapt to the
new multi-version path, resulting in many cases not triggering incremental clone.
This CL mainly modified:
1. Removed `incr_rs_meta` metadata
2. Modified the clone logic. When the clone is incremented, it will try to read the rowset in `stale_rs_meta`.
3. Delete a lot of code that was previously used for version compatibility.
NOTE: This patch would modify all Backend's data.
And this will cause a very long time to restart be.
So if you want to interferer your product environment,
you should upgrade backend one by one.
1. Refactoring be is to clarify the structure the codes.
2. Use unique id to indicate a rowset.
Nameing rowset with tablet_id and version will lead to
many conflicts among compaction, clone, restore.
3. Extract an rowset interface to encapsulate rowsets
with different format.
