enh: print_row str ends with 0

fix(query): fix special pseudo column caused taosd crash.

fix(wal): int overflow

feat(query): add mavg function

feat: stmt query test

feat: adjust query stmt APIs

fix(wal): int overflow

feat: tag read

fix: some problems of parser

feat(tsdb): unit of days and keep support minute

test: add test case for tmq

enh(tsdb): return oom err for submit msg

test: add ts filter testcases

fix(rpc): avoid fd leak