wayland/surface: Use transactions for all sub-surface hierarchy changes

And keep track of the hierarchy separately for the Wayland protocol and
for output. Protocol state is updated immediately as protocol requests
are processed, output state only when the corresponding transaction is
applied (which may be deferred until the next commit of the parent
surface).

v2:
* Directly add placement ops to a transaction, instead of going via
  pending_state.
* Use transaction entry for the sub-surface instead of that for its
  parent surface.
v3:
* Use transaction entry for the parent surface again, to ensure proper
  ordering of placement ops, and call
  meta_wayland_surface_notify_subsurface_state_changed only once per
  parent surface.
* Drop all use of wl_resource_add_destroy_listener, transactions are
  keeping surfaces alive as long as needed.
v4:
* Rebase on https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2501
* Drop ClutterActor code from meta_wayland_surface_apply_placement_ops.
  (Robert Mader)
v5:
* Rename MetaWaylandSubSurfaceState to MetaWaylandSurfaceSubState, since
  the next commit adds not sub-surface specific state to it.
v6:
* Move include of meta-wayland-subsurface.h from
  meta-wayland-transaction.c to .h, since the latter references
  MetaWaylandSubsurfacePlacementOp.
v7:
* Drop superfluous !entry check from meta_wayland_transaction_apply.
v8:
* Rename output/protocol fields to output/protocol_state. (Jonas Ådahl)
v9:
* Use meta_wayland_surface_state_new in
  meta_wayland_transaction_add_placement_op.
v10:
* Fix a few style issues per check-style.py.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>

src/wayland/meta-wayland-shell-surface.c

@@ -59,7 +59,8 @@ meta_wayland_shell_surface_calculate_geometry (MetaWaylandShellSurface *shell_su
     .height = meta_wayland_surface_get_height (surface),
   };
 
-  META_WAYLAND_SURFACE_FOREACH_SUBSURFACE (surface, subsurface_surface)
+  META_WAYLAND_SURFACE_FOREACH_SUBSURFACE (&surface->output_state,
+                                           subsurface_surface)
     {
       MetaWaylandSubsurface *subsurface;