feat: the unique function and tail function are rewritten as the corresponding clauses

refactor: remove duplicate conninfo in SRpcMsg

refactor(query): set correct buffer pages.

fix: mnode crash while sync reconfig

fix(query): set null for null value in groupby

fix: table merge scan sort buf size

fix: uncomment the codes of dropping stable

fix(query): adjust group limitation.

test: add auto exit case

refactor(sync): add syncIsReady