WorkSpace: UI filtering for add-ons

Allows for each workspace to have it's own add-ons on display.

Filtering for: Panels, Menus, Keymaps & Manipulators.
Automatically applies to add-ons at the moment.

Access from workspace, toggled off by default
once enabled, add-ons can be white-listed.

See D3076

source/blender/python/intern/bpy_rna.h

@@ -225,4 +225,8 @@ int pyrna_prop_validity_check(BPy_PropertyRNA *self);
 extern PyMethodDef meth_bpy_register_class;
 extern PyMethodDef meth_bpy_unregister_class;
 
+/* bpy.utils._bl_owner_(get/set) */
+extern PyMethodDef meth_bpy_owner_id_set;
+extern PyMethodDef meth_bpy_owner_id_get;
+
 #endif