We want to keep the wl_surface around, because surfaces create their
resources on construct and keep them until destroyed. See the HWND ond
Windows and the XWindow on X11.
This is relevant for graphics resources, where we want to have access
to the VkSurface and eglSurface while the GdkSurface is hidden.
We also want these surfaces to be permanent and not change during the
lifetime of the GdkSurface.
What we can - and must - destroy however are the xdg surfaces, because
those handle visibility on screen.
And we also need to ensure no buffer is attached, so that during the
next creation of the xdg surface we don't get a protocol error.
If we map, reposition, unmap, remap, the reposition feedback from the
last time a popup was mapped might be received while we're dealing with
the new version of the popup. At this point, the old reposition token
has no meating, so lets drop it. Also reset the reposition tokens when
creating new protocol objects, so that the reposition token are as if
we're in the initial state.
This fixes an issue where we'd get stuck if repeatedly smashing a button
that'd create popups that'd immediately get dismissed by the compositor.
