Implement stretch option for QS tiles

Rows with holes with stretch tiles to fill in empty spaces (except last row).
Edit mode reuses the same composable as InfiniteGridLayout, and the grid consistency interactor doesn't do any reordering.
This change also adds a layout selector to swap between prototypes.

Fix: 340246005
Flag: ACONFIG com.android.systemui.qs_ui_refactor DEVELOPMENT
Test: manually using layout selector on QSActivity

Change-Id: Ie4dbb81f99e3e6f0c00233974d518ec8b8612282