[td-6058]block union for nested query

* [TD-3197]<fix>: taosdemo and taosdump coverity scan issues.

* exit if read sample file failed.

* fix converity scan issue.

* fix coverity scan issue.

* fix coverity scan memory leak.

* fix resource leak reported by coverity scan.

* fix taosdemo coverity scan issue.

* fix tcsetattr and getchar return value determination bug.
Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

[TD-6068] <test> add test case for TD-6068

[TD-6011]<fix>: where clause including 'bool' Keyword causes core dump

[TD-6046]<fix> fix ts top/bottom/diff/derivative ts error

Format docs.md

* [TD-5844]<feature>: make cmd line parameter similar.

* fix test case align with taosdemo change.

* fix windows stack overflow issue.

* fix mac compile error.

* fix taosdemo cmdline parameter in tests/pytest/tools/taosdemoAllTest/NanoTestCase/taosdemoTestSupportNanoInsert.py

* make taos.exe use mysql style password input.

* make taos shell and taosdump use mysql style password input.

* determine scanf return value.

* cherry pick from develop/feature branch.

* cherry pick with ab6cde02

* cherry pick with d6bfe443Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

[TD-6155]<fix>:free tag expr at the end of sql parse

[td-6180]fix illegal sql issue

* cherry pick from develop branch.

* [TD-5136]<feature>: taosdemo simulate real senario.

* update test case according to taosdemo change

* adjust range of semi-random data.

* make demo mode use different tag name and value.

* change malloc to calloc for pid allocation.

* fix typo.

* fix binary length default value and group id logic.

* fix help msg.
Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

fix: fix altering schema  too much corrupting meta file

merge from cenc into master

[TD-6184]<enhance>: optimize insert from imported file

Feature/cenc

* [TD-5844]<feature>: make cmd line parameter similar.

* fix test case align with taosdemo change.

* fix windows stack overflow issue.

* fix mac compile error.

* fix taosdemo cmdline parameter in tests/pytest/tools/taosdemoAllTest/NanoTestCase/taosdemoTestSupportNanoInsert.py

* make taos.exe use mysql style password input.

* make taos shell and taosdump use mysql style password input.

* determine scanf return value.

* cherry pick from develop/feature branch.

merge from 2.0 branch

[TD-6020]fix taos crash issue