Brought the over-scroll effect found in the pinned quick settings panel to all the portrait mode quick settings states.
This helps improve the user experience while also bringing more consistency when pulling down the panel.

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.