Hi, this MR adds "clear all" and "do not disturb" buttons to `NotificationsWidget`.
Few other corrections have been made:
- Transitions should now work correctly, plus they can be disabled via `MobileShell.MobileShellSettings.animationsEnabled`;
- Loaders are now asynchronous;
- List items have now their own margins, in order to not clip their shadows.\
It only remains to implement a context menu to set do not disturb mode for a given period of time. I think it's a secondary feature on which we can work later, but in case tell me what to do.
Unfortunately I can't test the lockscreen on a phone at the moment, and I cannot take a performance test as well. It would be great if someone tested all these things, otherwise I'll provide as soon as possible.
Closes: https://invent.kde.org/plasma/plasma-mobile/-/issues/134
Move from a C++ library + QML plugin to a QML plugin only for simplicity, since the homescreen switching architecture will be done from Plasma, and so use of the shell library only needs to be from QML.
