fix(query): stddev function support unsigned data types

test：update testcase for function timediff() and timetruncate()

test: adjust valgrind cases

enh: refactor scheduler code

os: add file auto del func

fix(query): release memory when operator is destroyed.

refactor: adjust vnode propose msg

test: recover case

fix(query): set number of rows before assign column data.

fix:  avoid rpc mem leak

fix(query): add "1b" timeunit in function param to represent nanosecond

feat: push project condition down to its child