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

fix: fix page capacity calculation

feat(stream): stream partition by

os: add dll check

fix(query): remove group info during sort.

fix: not submit for stables without rollup in rsma database