not perform SDataRow/SKVRow convert anymore, utilize boundNullLen to facilitate the memRowType predict

* allocate enough buffer to accomodate tag data when get table meta from mnode

* accumulate affected rows count
Co-authored-by: Nshenglian zhou <slzhou@taosdata.com>

fix error, there is a core dump if tag equals a long num in where condition like where tag=99999999999999999999

fix error, there is a core dump if tag equals a long num in where condition like where tag=99999999999999999999