enh: comment off unused error codes in sync and wal

change learner config format

filter voter when agree upon

feat: support log slow query by default

enh: ignore single row null data type validation

remove null pointer

enh: support user passwd version

refactor: do some internal refactor and add the sample code.

enhance: error code refactor

fix/block-check-to-async-check

fix(stream): set the correct start offset for stream task.

fix: update commit index from heartbeat on  learner in the same way as on follower

fix: spool logging msg with pMsg->term in syncNodeOnHeartbeat