[Follow up] Allow user to customize battery charging threhsold.

As discussed in the following URL. #278 (comment 2551256)

Plasma provides an interface to allow users to override the battery charging threshold. The threshold value may be ready only and the configuration scheme is based on the vendor's rule in the firmware or driver. So, making a generic method to override the value is difficult. We need some ways to notify the user "the unexpected error is correct".