Hotfix/sangshuduo/td 6479 taosdump db seq (#7994)

* [TD-6479]<fix>: taosdump cmdline align for database sequence.

adopt 'taosdump -D db1,db2,...' format.

* fix core dump issue.

* refactor in progress

* heavily refactor in progress.

* change dumped filename back to thread index to avoid exceed file system limit.