Tool System: split UI label from tool identifiers

Prepare for exposing tool registration to the Python API.

- Generated tools can use their own prefix so naming collisions
  won't happen between hard coded & generated tools.
- Add-on authors can use the add-on name as a prefix.

Currently the names match, renaming will happen next.

release/scripts/startup/bl_ui/space_view3d.py

@@ -255,7 +255,9 @@ class VIEW3D_HT_header(Header):
             )
 
         if object_mode == 'PAINT_GPENCIL':
-            if context.workspace.tools.from_space_view3d_mode(object_mode).name == "Draw":
+            # FIXME: this is bad practice!
+            # Tool options are to be displayed in the topbar.
+            if context.workspace.tools.from_space_view3d_mode(object_mode).idname == "Draw":
                 settings = tool_settings.gpencil_sculpt.guide
                 row = layout.row(align=True)
                 row.prop(settings, "use_guide", text="", icon='GRID')