Rework layouts and base component of application delegate cards

Sad but true, Kirigami.AbstractCard is an over-complicated engineering effort, out of which we only really need its private background component. When it comes to content sizing management, it lacks required flexibility, which is why Discover components ended up abusing it with a fake content height and inner layout's vertical centering.

Until that is fixed upstream one way or another, the best we could do downstream is to take AbstractCard as a base (again, just for the sake of its background), and redo its content management. Which isn't too hard or complicated, so IMHO it's justified.

Application Delegate types got rid of hacks, and got a couple of improvements to their layouts, such as consistent margins, standard spacing on Row/ColumnLayout items, and icon animations disabled.

	Before	After
Grid
List +rating
List Installed
List Installed +compact