RFC: Use shared base class for status indicators

Use the same class as a base for battery, wifi, wwan and other status indicators. Since status icons should look all the same, using a common base class allows to share a lot of code. Also each quicksetting in the notification drawer should look and behave the same, therefore this implements the shared base for it.

Based on https://source.puri.sm/Librem5/phosh/merge_requests/401

This MR was opened to have a discussion on the idea, it currently updates wifiinfo and batteryinfo, but not wwaninfo (since there is currently some discussion https://source.puri.sm/Librem5/phosh/issues/141)

CC: @guido.gunther