Hotfix/sangshuduo/td 3985 taosdemo timestamp step overflow (#5951)

* [TD-3985]<fix>: taosdemo timestamp step overflow.

* fix specified subscribe test.

* replace potential overflow of int32 to int64

* replace potential int32 overflow variables to int64.

* replace potential int32 overflow variables to int64.
Co-authored-by: NShuduo Sang <sdsang@taosdata.com>