kms: Only emit resources-changed signal if we recorded a change

Since we cache already all the KMS parameters we care about let's check at
each device update if anything has really changed and only in such case
emit a resources-changed signal.

In this way we can also filter out the DRM parameters that when changed
don't require a full monitors rebuild.

Examples are the gamma settings or the privacy screen parameters, that
emits an udev "hotplug" event when changed, but we want to register those
only when we handle the changed property.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1964>

src/backends/meta-output.h

@@ -106,6 +106,10 @@ typedef struct _MetaOutputInfo
   MetaTileInfo tile_info;
 } MetaOutputInfo;
 
+gboolean
+meta_tile_info_equal (MetaTileInfo *a,
+                      MetaTileInfo *b);
+
 #define META_TYPE_OUTPUT_INFO (meta_output_info_get_type ())
 META_EXPORT_TEST
 GType meta_output_info_get_type (void);