bone constraints settings
'UI_context_copy_to_selected_list()' was working fine for constraints on
objects (would properly get the path and list of selected objects) and
also for bone settings (would properly get the path and list of bones).
There was no special case for constraints on bones though, so code would
work on selected objects (not selected bones).
So we now get the right bones and resolve the path to the constraint
setting _from the bones_.
Maniphest Tasks: T74006
Differential Revision: https://developer.blender.org/D6897
f2224ccfce