gh-101766: Fix refleak for _BlockingOnManager resources from test suite level (gh-101988)

Author: corona10

Lib/importlib/_bootstrap.py

@@ -85,11 +85,6 @@ def __enter__(self):
     def __exit__(self, *args, **kwargs):
         """Remove self.lock from this thread's _blocking_on list."""
         self.blocked_on.remove(self.lock)
-        if len(self.blocked_on) == 0:
-            # gh-101766: glboal cache should be cleaned-up
-            # if there is no more _blocking_on for this thread.
-            del _blocking_on[self.thread_id]
-            del self.blocked_on
 
 
 class _DeadlockError(RuntimeError):

Lib/test/test_importlib/test_locks.py

@@ -33,6 +33,11 @@ class ModuleLockAsRLockTests:
     test_repr = None
     test_locked_repr = None
 
+    def tearDown(self):
+        for splitinit in init.values():
+            splitinit._bootstrap._blocking_on.clear()
+
+
 LOCK_TYPES = {kind: splitinit._bootstrap._ModuleLock
               for kind, splitinit in init.items()}