feat: create mnode

refactor(stream): remove out-of-date msg

fix(query): fix first(*) result incorrect for all NULL entry tables

fix(query): fix elapsed function time_unit cannot be smaller than db precision

fix(query): fix avg/sum function result overflown output inf/nan

fix(stream): double free

fix(query): remove redundant definition of stream table in mnode.

enh: add column length error retry

fix(query): add finalize for first function.

test: case for alter stable

fix(query): prepare enough buffer before convert string.

refactor: use tagver and colver insteadof sversion

feat: scheduler async api

TD-15957

fix(stream): function error