Gizmo: support for gizmo-group properties

This allows gizmo groups to store properties in the tool.
This makes sense for gizmo options which only control gizmo display and
don't control operator execution.

Unlike similar kinds of properties,
this isn't accessible via the gizmo-group-type instance.

For now the it's only stored in the workspace tool as can be done for
operator properties, so each instance doesn't have different settings
which would be confusing from a user perspective and complicate access
from the top-bar.

Later we could add gizmo-group properties if needed.

source/blender/python/intern/bpy_gizmo_wrap.c

@@ -192,37 +192,30 @@ void BPY_RNA_gizmo_wrapper(wmGizmoType *gzt, void *userdata)
 
 static void gizmogroup_properties_init(wmGizmoGroupType *gzgt)
 {
-#ifdef USE_SRNA
 	PyTypeObject *py_class = gzgt->ext.data;
-#endif
 	RNA_struct_blender_type_set(gzgt->ext.srna, gzgt);
 
-#ifdef USE_SRNA
 	/* only call this so pyrna_deferred_register_class gives a useful error
 	 * WM_operatortype_append_ptr will call RNA_def_struct_identifier
 	 * later */
-	RNA_def_struct_identifier(gzgt->srna, gzgt->idname);
+	RNA_def_struct_identifier_no_struct_map(gzgt->srna, gzgt->idname);
 
 	if (pyrna_deferred_register_class(gzgt->srna, py_class) != 0) {
 		PyErr_Print(); /* failed to register operator props */
 		PyErr_Clear();
 	}
-#endif
 }
 
 void BPY_RNA_gizmogroup_wrapper(wmGizmoGroupType *gzgt, void *userdata)
 {
 	/* take care not to overwrite anything set in
 	 * WM_gizmomaptype_group_link_ptr before opfunc() is called */
-#ifdef USE_SRNA
 	StructRNA *srna = gzgt->srna;
-#endif
 	*gzgt = *((wmGizmoGroupType *)userdata);
-#ifdef USE_SRNA
 	gzgt->srna = srna; /* restore */
-#endif
 
-#ifdef USE_SRNA
+	/* don't do translations here yet */
+#if 0
 	/* Use i18n context from ext.srna if possible (py gizmogroups). */
 	if (gzgt->ext.srna) {
 		RNA_def_struct_translation_context(gzgt->srna, RNA_struct_translation_context(gzgt->ext.srna));