fix:Explicit null dereferenced

enh: last cache optimize

fix(stream): heap uaf

docs: add StackOverflow link

test: add asan case and adjust python test frame

fix(query): fix error in seq fetch data block.

refactor(sync): add timestamp trace log when elect and heartbeat

test: add asan case

test: adjust asan case

fix(shell): add help command and fix create table filed complete

refactor: enable continue query when the buffer of sink node is empty