Split the app grid out from the overview

This:

• replaces the scrollable app grid from the overview by a paginated app carousel
• puts the app carousel in a page below the overview
• moves the favorites at the beginning of the app carousel
• moves the search bar above the running apps so we can display the results without having UI elements jumping around

It's still a prototype and I'm polishing it, but if you want you can already pick the package from the CI and try it on PureOS Byzantium with https://source.puri.sm/Librem5/developer.puri.sm/-/issues/193.

Please note there are some known and likely unknown regressions, so test it at your own risk while I polish it.

What it looks like at the creation of the MR:

phosh-2steps-app-drawer-prototype

To do:

• Refiltering the paginated apps list (to show/hide non-adpative apps) freezes the UI because it infinitely loops in the apps model somehow, it should be fixed.
• Allow quitting the search mode: hiding the OSK, unfocusing the search bar…
• The OSK hides the bottom of the app search results, it should be fixed.
• The apps carousel's indicator is wrongly sized on my phone but not on my dev environment, it should be fixed.
• Refilter the apps carousel when favorites change.
• Reset the drawer's state when it's folded
• Prevent dragging the surface when dragging a PhoshActivity.
• layout on wider screens (including landscape): !1079 (comment 1478365)
• crash: !1079 (comment 1493563)
• performance regressions: !1079 (comment 1523765)

Helps #208