`test_capi`: `test_threadstate_set_stack_protection` is flaky on Azure CI

Bug report

Bug description:

test.test_capi.test_misc.Test_testinternalcapi.test_threadstate_set_stack_protection fails on Azure Pipeline.

For example in this run https://dev.azure.com/Python/cpython/_build/results?buildId=173303:

test_threadstate_set_stack_protection (test.test_capi.test_misc.Test_testinternalcapi.test_threadstate_set_stack_protection) ... Assertion failed: ts->c_stack_soft_limit < ts->c_stack_top, file D:\a\1\s\Modules\_testinternalcapi.c, line 3045
Fatal Python error: Aborted

Current thread 0x000011f0 (most recent call first):
  File "D:\a\1\s\Lib\unittest\case.py", line 637 in _callTestMethod
  File "D:\a\1\s\Lib\unittest\suite.py", line 122 in run
  File "D:\a\1\s\Lib\unittest\suite.py", line 84 in __call__
  File "D:\a\1\s\Lib\unittest\runner.py", line 256 in run
  File "D:\a\1\s\Lib\test\libregrtest\single.py", line 84 in _run_suite
  File "D:\a\1\s\Lib\test\libregrtest\single.py", line 42 in run_unittest
  File "D:\a\1\s\Lib\test\libregrtest\single.py", line 162 in test_func
  File "D:\a\1\s\Lib\test\libregrtest\single.py", line 118 in regrtest_runner
  File "D:\a\1\s\Lib\test\libregrtest\single.py", line 165 in _load_run_test
  File "D:\a\1\s\Lib\test\libregrtest\single.py", line 210 in _runtest_env_changed_exc
  File "D:\a\1\s\Lib\test\libregrtest\single.py", line 319 in _runtest
  File "D:\a\1\s\Lib\test\libregrtest\single.py", line 348 in run_single_test
  File "D:\a\1\s\Lib\test\libregrtest\worker.py", line 99 in worker_process
  File "D:\a\1\s\Lib\test\libregrtest\worker.py", line 137 in main
  File "D:\a\1\s\Lib\test\libregrtest\worker.py", line 141 in <module>
  File "<frozen runpy>", line 87 in _run_code
  File "<frozen runpy>", line 201 in _run_module_as_main

Current thread's C stack trace (most recent call first):
  <cannot get C stack on this system>

Extension modules: _testcapi, _testlimitedcapi, _testinternalcapi, _testmultiphase, _testsinglephase, _testbuffer (total: 6)

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows

Start with test.test_capi.test_misc.Test_testinternalcapi.test_threadstate_set_stack_protection and inspect Modules/_testinternalcapi.c around line 3045, where the Azure Windows assertion fails. Reproduce the named test in the Azure environment and trace the stack-limit values involved. Done means the test passes reliably on Azure without the assertion failure.