#34778#34849
fix two problems:
1. count(*) incorrect, if growing insert duplicated (pk, timestamp)
pairs that pk and timestamp all same, need to keep just one pair.
2. count(*) may core dump, if get_real_count interface get snapshot and
do mvcc at not consistency status, mainly happens under concurrency.
Signed-off-by: luzhang <luzhang@zilliz.com>
Co-authored-by: luzhang <luzhang@zilliz.com>