This commit changes the behavior of `new_*` signals to better match
their names (see https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3608).
wlr_xdg_shell.events.new_surface is now emitted when an xdg_surface is
created, and wlr_xdg_shell.events.new_{toplevel,popup} events are
introduced to get notified when an xdg_{toplevel,popup} is created.
Same applies to
`wlr_xdg_decoration_manager_v1.events.new_toplevel_decoration`. As a
result, wlr_xdg_surface.added and wlr_xdg_toplevel_decoration_v1.added
are removed, as we no longer need to track whether the corresponding
event was emitted.
Additionally, this commit changes the behavior of
wlr_xdg_surface.events.destroy: it is now emitted when the xdg_surface
is destroyed, as the name suggests.
wlr_xdg_{toplevel,popup}.events.destroy events are added to get
notified when an xdg_{toplevel,popup} is destroyed.
Some globals are static and it doesn't make sense to destroy them before
the wl_display. For instance, wl_compositor should be created before the
display is started and shouldn't be destroyed.
For these globals, we can simplify the code by removing the destructor
and stop keeping track of wl_resources (these will be destroyed with the
wl_display by libwayland).
This requires functions without a prototype definition to be static.
This allows to detect dead code, export less symbols and put shared
functions in headers.