[2/N] (Handle Menu) Better encapsulation of window decor's views

Moves click detection out of the DesktopModeWindowDecorViewModel
and into the HandleMenuView.

The goal here is to keep implementation details of the menu view
encapsulated (resource ids, gesture detection, styling, etc), and
provide the decoration/viewmodel with abstractions for actions taken by
the user on the view (e.g. #setOnToDesktopClickListener).

Flag: EXEMPT refactor
Bug: 346441962
Test: with additional view container flag enabled & disabled - check
HandleMenu works as usual (clicks, animations, fullscreen/freeform)
Test: atest WMShellUnitTests

Change-Id: I003c0d5cc042dd9a53c6f1800a8191cd84dc2b87