Use the availability of a tile as a key for the grouped and sorted list in edit mode

This also passes the entire list of tiles to Edit mode instead of splitting and rejoining the list.
The AvailableTileGridCell data class is also removed as it's no longer needed.

Flag: com.android.systemui.qs_ui_refactor_compose_fragment
Fixes: 405279487
Test: DragAndDropTest.kt
Test: EditModeTest.kt
Test: ResizingTest.kt
Change-Id: Ieb085569fe4d82bc9c7f21651ef8c44474f59ca4