[td-6282]fix nested query no return issue

[TD-6264]<hotfix>:backport _block_dist() from 2.1 to 2.0 to fix core …

[TD-6264]<hotfix>:backport _block_dist() from 2.1 to 2.0 to fix core dump due to tbuf length limitation

[ci skip] update scirpt for csv generator

change version numbe ver 2.0.20.15

[TD-6176]<test> add stmt query test script

[TD-6209]<test>add case for TD-6027

[TD-6214]<feature> improve insert performance 

change version number

[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-6229] enable the last_row cache while query condition exists.

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

[TD-6164]<fix>: fix deadlock with fopen's malloc

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

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

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

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