docs/zh_CN: add the translation of kbuild/kconfig.rst

Finish the translation of kbuild/kconfig.rst and move kconfig
from TODO to the main body.

Update to commit f6314b76 ("docs: kbuild/kconfig: reformat/cleanup")

Signed-off-by: Dongliang Mu <dzm91@hust.edu.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20241005144121.3953919-1-dzm91@hust.edu.cn