Use spy windows to resize tasks

This CL does a few things to achieve the goal:

1. It converts the input windows of decor container layers to spy
   windows, so that input windows behind them can receive input events
   at the same time. This is what allows the close button in the caption
   to receive mouse clicks even if the mouse clicks in the intersected
   area of the close button and the square top-right touch resize
   handle.
2. It adds task input sinks behind decor container layers, so that
   motion events received by resize handlers out of task windows won't
   be dispatched to windows behind the resize handlers. I chose to put
   the task input sinks under the decor container layers so that the
   logic can be mostly limited inside DragResizeInputListener.
3. Resize handlers pilfer events when they decide to handle resize
   gestures. Windows that received the same gesture will receive a
   cancelled event.

There are a few remaining issues:

1. We update mouse cursors whenever the resize handlers receive hover
   events. We should avoid updating them when they aren't supposed to
   to resize task windows if the resize is started at the hover events,
   so windows behind the resize handlers have chances to update the
   mouse cursor shape.
2. The mouse cursor shape are updated to double arrows if the mouse
   hovers in corner areas that are slightly over task radii inward to
   one side of the task bounds, and less than corner sizes inward to
   an adjacent side of the task bounds. However this place is completely
   inside the task bounds, so we shouldn't resize the task at all with
   mice.

This CL also changes the CtrlType annotation to be flags.

Bug: 266866903
Test: Close buttons in captions be clicked when the mouse cursor is
close to the corner.

Change-Id: I28215f1dc51bfaaccfd5fa4856186f4a6f0e4925