fix: some problems of tag query and sma

refactor(cluster): adjust mnode sync codes

fix(query): copy the hasNull attribute to destination SColumnInfoData.

fix(sync): show vgroups all leader

feat(tmq): support show

refactor: vnode

feat: handle null value

fix(shell): memory free error.

fix: allow startup if the log directory does not exist

fix(query): add an null ptr check

enh: add flag in syncEnv, to deal with expired timer

fix(query): fix taosshell crash when arithmetic operation with NULL concstant

fix: set ready status while alterdb