docs/zh_CN: create new translations for zh_CN/dev-tools/testing-overview

Create new translations for dev-tools/testing-overview.rst and link it
to dev-tools/index.rst with TODOList modifications.

Signed-off-by: Hu Haowen <src.res@email.cn>
Reviewed-by: Wu XiangCheng <bobwxc@email.cn>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Wu XiangCheng <bobwxc@email.cn>
Link: https://lore.kernel.org/r/20210620052841.GA22083@bobwxc.top


Signed-off-by: Jonathan Corbet <corbet@lwn.net>