* restore .gitmodules

* Revert "[TD-13408]<test>: move tests directory out"

This reverts commit 7db7bd9337cedc4cd0e3f3b16618b97d09791eaa.

* revert to make tests back

* immigrate file change in stand-alone repo to TDengine

* remove tests repository checkout
Co-authored-by: Ntangfangzhi <fztang@taosdata.com>