window: Make propagate_focus_appearance internal to MetaWindow

It's an internal helper function. The public interface is
meta_window_activate or meta_window_focus.
Rework timestamp pinging

If a window temporarily goes unresponsive, and then returns later, we
should hide the kill dialog that we showed to the user.
place: Simplify control flow and fix a crash
place: Move maximization path above first fit finding
place: Don't require checking for changing

The only time this can change is if find_first_fit returns TRUE,
at which point we already jump out.
core: Remove some unused meta_core_get requests
window: Move _NET_WM_DESKTOP setting to window-x11
window-x11: Make sure to chain up in grab_op_began / ended

To make sure shaken_loose gets reset.
window-wayland: Change the state on grab op transitions

This could affect the RESIZING state.
window: Move meta_window_wayland_new to window-wayland.c
window: Move constructors to the respective header files
window: Make border_width private to X11