gh-142418: Remove unnecessary cycle detection from _has_coroutine_mark

Partial and method objects cannot form reference cycles in this context, so
the cycle-detection logic in _has_coroutine_mark introduced unnecessary
overhead. This change removes the visited-set check and keeps the function
as a simple unwrapping loop while still correctly detecting explicitly
marked coroutine wrappers.

Author: Joshua-Ward1

Lib/inspect.py

@@ -306,12 +306,7 @@ def isgeneratorfunction(obj):
 _is_coroutine_mark = object()
 
 def _has_coroutine_mark(f):
-    visited = set()
     while True:
-        if id(f) in visited:
-            return False
-        visited.add(id(f))
-
         if getattr(f, "_is_coroutine_marker", None) is _is_coroutine_mark:
             return True