[3.15] Fix _PyThreadState_ResumeDetached() assertion with attach waiters

[nascheme]

Make _PyThreadState_ResumeDetached() waiter-aware and use it from start_the_world(), matching main branch. Remove tstate_resume().

This fixes a broken backport and should fix broken CI tests. The backport PR is GH-158186.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot aarch64 CentOS9 3.15 (tier-1) has failed when building commit ef498e0.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/2176/builds/396) and take a look at the build logs.
4. Check if the failure is related to this commit (ef498e0) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/2176/builds/396

Failed tests:

• test_cext

Failed subtests:

• test_build - test.test_cext.TestPublicC.test_build

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/runtests.py", line 68, in <module>
    main()
    ~~~~^^
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/runtests.py", line 62, in main
    raise AssertionError(f'Tests leaked {diff} references')
AssertionError: Tests leaked 1 references
ERROR


Traceback (most recent call last):
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/__init__.py", line 114, in test_build
    self.check_build('_test_cext')
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/__init__.py", line 106, in check_build
    run_cmd('Tests', cmd)
    ~~~~~~~^^^^^^^^^^^^^^
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/__init__.py", line 81, in run_cmd
    subprocess.run(cmd, check=True, env=env)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/subprocess.py", line 692, in run
    raise CalledProcessError(retcode, process.args,
                             output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command ['/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/build_oot/build/test_python_2529270æ/tempcwd/env/bin/python', '-X', 'dev', '/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/runtests.py', '_test_cext'] returned non-zero exit status 1.


Traceback (most recent call last):
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/__init__.py", line 114, in test_build
    self.check_build('_test_cext')
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/__init__.py", line 106, in check_build
    run_cmd('Tests', cmd)
    ~~~~~~~^^^^^^^^^^^^^^
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/__init__.py", line 81, in run_cmd
    subprocess.run(cmd, check=True, env=env)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/subprocess.py", line 692, in run
    raise CalledProcessError(retcode, process.args,
                             output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command ['/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/build_oot/build/test_python_2571427æ/tempcwd/env/bin/python', '-X', 'dev', '/var/lib/buildbot/worker/cstratak-CentOS9-aarch64/3.15.cstratak-CentOS9-aarch64/build/Lib/test/test_cext/runtests.py', '_test_cext'] returned non-zero exit status 1.

[nascheme]

This PR should fix GH-159373.