qa: `p2p_ibd_stalling.py --v1transport` fails #32090

https://github.com/hebasto/bitcoin-core-nightly/actions/runs/13914507401/job/38935007425:

320/321 - p2p_ibd_stalling.py --v1transport failed, Duration: 484 s

stdout:
2025-03-18T04:03:23.417000Z TestFramework (INFO): PRNG seed is: 8897219840825193112
2025-03-18T04:03:23.418000Z TestFramework (INFO): Initializing test directory /home/runner/work/bitcoin-core-nightly/bitcoin-core-nightly/test_runner_₿_🏃_20250318_034132/p2p_ibd_stalling_112
2025-03-18T04:03:23.719000Z TestFramework (INFO): Prepare blocks without sending them to the node
2025-03-18T04:03:23.783000Z TestFramework (INFO): Check that a staller does not get disconnected if the 1024 block lookahead buffer is filled
2025-03-18T04:03:26.061000Z TestFramework (INFO): Check that increasing the window beyond 1024 blocks triggers stalling logic
2025-03-18T04:03:26.876000Z TestFramework (INFO): Check that the stalling peer is disconnected after 2 seconds
2025-03-18T04:11:26.898000Z TestFramework.utils (ERROR): wait_until() failed. Predicate: ''''
        def test_function():
            if check_connected:
                assert self.is_connected
            return test_function_in()
'''
2025-03-18T04:11:26.898000Z TestFramework (ERROR): Assertion failed
Traceback (most recent call last):
  File "/home/runner/work/bitcoin-core-nightly/bitcoin-core-nightly/test/functional/test_framework/test_framework.py", line 135, in main
    self.run_test()
    ~~~~~~~~~~~~~^^
  File "/home/runner/work/bitcoin-core-nightly/bitcoin-core-nightly/build/test/functional/p2p_ibd_stalling.py", line 105, in run_test
    peers[0].wait_for_disconnect()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/runner/work/bitcoin-core-nightly/bitcoin-core-nightly/test/functional/test_framework/p2p.py", line 608, in wait_for_disconnect
    self.wait_until(test_function, timeout=timeout, check_connected=False)
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/bitcoin-core-nightly/bitcoin-core-nightly/test/functional/test_framework/p2p.py", line 600, in wait_until
    wait_until_helper_internal(test_function, timeout=timeout, lock=p2p_lock, timeout_factor=self.timeout_factor, check_interval=check_interval)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/bitcoin-core-nightly/bitcoin-core-nightly/test/functional/test_framework/util.py", line 317, in wait_until_helper_internal
    raise AssertionError("Predicate {} not true after {} seconds".format(predicate_source, timeout))
AssertionError: Predicate ''''
        def test_function():
            if check_connected:
                assert self.is_connected
            return test_function_in()
''' not true after 480.0 seconds
2025-03-18T04:11:26.962000Z TestFramework (INFO): Not stopping nodes as test failed. The dangling processes will be cleaned up later.

System: NetBSD 10.1.

2025-03-18T04:11:27.6410272Z  node0 2025-03-18T04:03:24.307185Z (mocktime: 2025-03-18T04:03:24Z) [msghand] [net_processing.cpp:3379] [ProcessMessage] [net] received: headers (82947 bytes) peer=1
(...)
2025-03-18T04:11:27.8241273Z  node0 2025-03-18T04:03:24.387659Z (mocktime: 2025-03-18T04:03:24Z) [msghand] [net_processing.cpp:3379] [ProcessMessage] [net] received: headers (82947 bytes) peer=0 

Reason is that the headers messages are received in a different order than they are sent, and as a result of that later the wrong peer is marked for stalling. I opened #32148 adding a sync.