Bug 1667851 [Wayland] Rework mozcontainer wl_subsurface creation, r=jhorak

Rework wl_subsurface creation in these steps:

1) moz_container_wayland_size_allocate() handler is called when
   mContainer size/position is known.
   It calls moz_container_wayland_surface_create_locked(), registers
   a frame callback handler
   (moz_container_wayland_frame_callback_handler()).

2) moz_container_wayland_frame_callback_handler() is called
   when wl_surface owned by mozContainer is ready.
   We call initial_draw_cbs() handler and we can create our wl_subsurface
   on top of wl_surface owned by mozContainer.

Also size wl_buffer at WindowSurfaceWayland according to mozcontainer size,
don't use nsWindow bounds for it.

Differential Revision: https://phabricator.services.mozilla.com/D104549

Author: stransky