WIP: Homescreen

Tasks:

• Change the "grid" part of the homescreen into an application list drawer

• There would be no "in between" state between the drawer being closed and it being open
• If there aren't enough elements to justify opening the panel fullscreen, only show the panel as much as it needs to be (like how it works right now)

• Add support for desktop pages https://invent.kde.org/plasma/plasma-phone-components/-/issues/38
• Add support for application folders on desktop https://invent.kde.org/plasma/plasma-phone-components/-/issues/41
• Rework applicationlistmodel to support the above features
• Add new settings for # of rows, # of columns on desktop, so that the layout is not messed up on screen rotate