The TiKV may return wrong `_tidb_commit_ts` for point-get and reverse-scan

See #19374 

This issue does not introduce any release bugs actually, because `_tidb_commit_ts` is used in feature branch only.

Problem Summary:

When `load_commit_ts=true` and a key has newer committed `Op_Lock` versions on top of the visible `Op_Put`, TiKV may return the lock commit_ts instead of the put commit_ts.

