desktop-exploded-view: Initial implementation

This is an initial implementation of the desktop exploded view. The
layout algorithm (implemented in OrganizeDesktopTasksUseCase) is
currently a basic placeholder.

Flag: com.android.launcher3.enable_desktop_exploded_view
Test: Manual
Bug: 367353392

Change-Id: I6826a2583a3e0027c809d4fd3b9bab716f2f3b72