bpo-39984: Pass tstate to _PyEval_SignalAsyncExc()

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_PyEval_SignalAsyncExc() and _PyEval_FiniThreads() now expect
tstate, instead of ceval.

https://bugs.python.org/issue39984

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macOS CI failed with:

FAIL: test_daemon_threads_shutdown_stdout_deadlock (test.test_io.CMiscIOTest)
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Traceback (most recent call last):
  File "/Users/runner/runners/2.165.2/work/cpython/cpython/Lib/test/test_io.py", line 4260, in test_daemon_threads_shutdown_stdout_deadlock
    self.check_daemon_threads_shutdown_deadlock('stdout')
  File "/Users/runner/runners/2.165.2/work/cpython/cpython/Lib/test/test_io.py", line 4255, in check_daemon_threads_shutdown_deadlock
    self.assertRegex(err, pattern)
AssertionError: Regex didn't match: "Fatal Python error: _enter_buffered_busy: could not acquire lock for <(_io\\.)?BufferedWriter name='<stdout>'> at interpreter shutdown, possibly due to daemon threads" not found in 'Fatal Python error: Segmentation fault\n\n'

Ubuntu CI failed with:

======================================================================
FAIL: test_mymanager (test.test_multiprocessing_spawn.WithManagerTestMyManager)
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Traceback (most recent call last):
  File "/home/runner/work/cpython/cpython/Lib/test/_test_multiprocessing.py", line 2847, in test_mymanager
    self.assertIn(manager._process.exitcode, (0, -signal.SIGTERM))
AssertionError: -11 not found in (0, -15)

======================================================================
FAIL: test_mymanager_context (test.test_multiprocessing_spawn.WithManagerTestMyManager)
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Traceback (most recent call last):
  File "/home/runner/work/cpython/cpython/Lib/test/_test_multiprocessing.py", line 2855, in test_mymanager_context
    self.assertIn(manager._process.exitcode, (0, -signal.SIGTERM))
AssertionError: -11 not found in (0, -15)

======================================================================
FAIL: test_mymanager_context_prestarted (test.test_multiprocessing_spawn.WithManagerTestMyManager)
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Traceback (most recent call last):
  File "/home/runner/work/cpython/cpython/Lib/test/_test_multiprocessing.py", line 2862, in test_mymanager_context_prestarted
    self.assertEqual(manager._process.exitcode, 0)
AssertionError: -11 != 0

Not good.

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I wrote PR #19054 to fix these crashes.