remove 3.9 bw compat In cw 3.9, interfaces are deprecated and replaced with adapters, yielding a lot of bw compat in many places -- most if this patch is concerned with the interface bw compat - cwvreg: interface cleanup - doc/adapters.rst: interface cleanup - entities/adapters.py, wfobjs.py: interfaces bw compat - entity.py: interfaces bw compat, also get_value, delete, attr_metadata, has_perm, set_related_cache, clear_related_cache, clear_related_cache, related_rql - predicates.py: score_interfaces & implements - interfaces.py & mixins.py: 100% gone - view.py: implement_adapter_compat, unwrap_adapter_compat - calendar.py, editcontroller.py, ibreadcrumbs.py, navigation.py, xmlrss.py: interface bw compat - treeview.py: salvage one function from mixins.py Related to #2782004.