In vertical base compaction, same rows will be filtered in vertical_merge_iterator,
we should skip these filtered rows when set agg flag of delete sign.
For example, schema is a,b,delete_sign, and data is
1,1,1
1,1,0
1,1,0
2,2,1
2,2
and Block we get in VerticalBlockReader is
1,1,1
2,2,1
and we should set agg flag idex 0,4 to true when handle delete sign, so
we add a function continuous_agg_count to skip same rows filtered in
VerticalMergeIterator.
fix a dcheck error for vertical compaction on Merge-On-Write table。
When merge rowsets with empty segment, VerticalHeapMergeIterator::init
return ok directly and _record_rowids not set, dcheck failed when
_unique_key_next_block call current_block_row_locations。
