enh: refactor the code to create and delete mnodes

feat(shell): modify introduction for auto tab completion

enh(query): opt group by tag perf.

refactor:do some internal refactor to optimize the query performance.

fix: fix kill query crash issue

fix: change schema-less describtion to reduce ambiguity

fix: taos-sql/functions document error

fix(stream): memory leak

fix(stream):Defects Tracking, delete log

enh: do coverity scan

docs: fix 'terminate a tuery' chapter

fix: converity scan problem

fix(tmq): push msg