move name_asyncgen later than self.foreign.remove

as it's critical that self.foriegn.remove runs

Author: graingert

src/trio/_core/_asyncgens.py

@@ -80,14 +80,14 @@ def finalize_in_trio_context(
                 self.trailing_needs_finalize.add(agen)
 
         def finalizer(agen: AsyncGeneratorType[object, NoReturn]) -> None:
-            agen_name = name_asyncgen(agen)
             try:
                 self.foreign.remove(id(agen))
             except KeyError:
                 is_ours = True
             else:
                 is_ours = False
 
+            agen_name = name_asyncgen(agen)
             if is_ours:
                 runner.entry_queue.run_sync_soon(
                     finalize_in_trio_context,