Replaces arrange_windows() with arrange_root(), arrange_output(),
arrange_workspace() and arrange_children_of().
Also makes fullscreen views save and restore their dimensions, which
allows it to preserve any custom resize and is also a requirement for
floating views once they are implemented.
The exact semantics of this command are complicated. I'll describe each
test scenario as s-expressions. Everything assumes L_HORIZ if not
specified, but if you rotate everything 90 degrees the same test cases
hold.
```
(container (view a) (view b focus) (view c))
-> move left
(container (view b focus) (view a) (view c))
(container (view a) (view b focus) (view c))
-> move right
(container (view a) (view c) (view b focus))
(container L_VERT (view a))
(container L_HORIZ
(view b) (view c focus))
-> move up
(container L_VERT
(view a) (view c focus))
(container L_HORIZ (view b))
(workspace
(view a) (view b focus) (view c))
-> move up
(workspace [split direction flipped]
(view b focus)
(container (view a) (view c)))
(workspace
(view a) (view b focus) (view c))
-> move down
(workspace [split direction flipped]
(container (view a) (view c))
(view b focus)))
Note: outputs use wlr_output_layout instead of assuming that i+/-1 is
the next output in the move direction.
(root
(output X11-1
(workspace 1))
(output X11-2
(workspace 1 (view a focus) (view b)))))
-> move left
(root
(output X11-1
(workspace 1 (view a focus)))
(output X11-2
(workspace 1 (view b)))))
(root
(output X11-1
(workspace 1
(container (view a) (view b)))
(output X11-2
(workspace 1 (view c focus)))))
-> move left
(root
(output X11-1
(workspace 1
(container (view a) (view b))
(view c focus)))
(output X11-2
(workspace 1)))
```
