bpo-43960: test_pdb resets breakpoints (GH-25673)

Reset global breakpoint state at the beginning of
test_pdb_next_command_in_generator_for_loop() to make it deterministic.

Lib/test/test_pdb.py

@@ -1192,6 +1192,7 @@ def test_pdb_next_command_in_generator_for_loop():
     ...         print('value', i)
     ...     x = 123
 
+    >>> reset_Breakpoint()
     >>> with PdbTestInput(['break test_gen',
     ...                    'continue',
     ...                    'next',