* [TD-5398]<fix>: taosdemo 4096 columns table creation failed.

* change column name prefix from col to c for maxium column number to fix buffer length.

* use accurate buffer length.

* fix test case for column name be shorter.
Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

* 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.

btw, solve two taosdemo test cases too.

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

change focal to bionic.

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

install python3.8

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

install python3.8 and pip, setuptools

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

install python3.8, and install pip and setuptools

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

modify smoketest.sh to python3.8

* fix timezone build error with clang/linux.

* change fixed version python 3.8 to 3.
Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

[TD-4422]-adding test cases for different combination of drop, child_table_exist, and auto_create_table