build: release ver-3.0.4.2

fix: alter dnode option has no effect

Remove taosx, connector, explorer and taoskeeper in cloud tdengine

fix:lost data because tsdbreader or task is killed

update crash_gen

fix:remove get schema from previous for taosx

add parameter

fix:set task code success after kill

fix: select last(*) ..group by tag return wrong rows of data

schema much change and schemaless insert test case

* docs: update readme with libgflags

* docs: update README-CN.md

fix:error in pHandle lock

fix: result block ensure capacity when finalize may produce serveral …

fix:core dump in tsdbreader is null when tsdbreader is closed by subscribe msg and current offset equal to saved

fix(query): do some internal refactor, and fix the bug when calender duration exists in sliding and offset.

fix: distinct wrong result issue

fix(query): add null check.