gh-109693: Remove pycore_atomic_funcs.h

[colesbury]

Use functions from pyatomic.h instead.

• Issue: Clean-up pyatomic headers #109693

[vstinner]

LGTM.

Sure, I was awaiting this PR! :-) Include/internal/pycore_atomic_funcs.h is only used by _PyUnicode_FromId() as you noticed :-)

[vstinner]

Merged, thanks.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot s390x SLES 3.x has failed when building commit 2aceb21.

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/all/#builders/540/builds/6591) and take a look at the build logs.
4. Check if the failure is related to this commit (2aceb21) 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/all/#builders/540/builds/6591

Failed tests:

• test_tools

Failed subtests:

• test_freeze_simple_script - test.test_tools.test_freeze.TestFreeze.test_freeze_simple_script

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

==

Click to see traceback logs

Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-sles-z/build/Lib/test/test_tools/test_freeze.py", line 32, in test_freeze_simple_script
    outdir, scriptfile, python = helper.prepare(script, outdir)
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/dje/cpython-buildarea/3.x.edelsohn-sles-z/build/Tools/freeze/test/freeze.py", line 146, in prepare
    copy_source_tree(srcdir, SRCDIR)
  File "/home/dje/cpython-buildarea/3.x.edelsohn-sles-z/build/Tools/freeze/test/freeze.py", line 95, in copy_source_tree
    shutil.copytree(oldroot, newroot, ignore=ignore_non_src)
  File "/home/dje/cpython-buildarea/3.x.edelsohn-sles-z/build/Lib/shutil.py", line 588, in copytree
    return _copytree(entries=entries, src=src, dst=dst, symlinks=symlinks,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/dje/cpython-buildarea/3.x.edelsohn-sles-z/build/Lib/shutil.py", line 542, in _copytree
    raise Error(errors)
shutil.Error: [('/home/dje/cpython-buildarea/3.x.edelsohn-sles-z/build/build/test_python_50750æ', '/tmp/test_python_jzsirdzs/tmpikgre5sn/cpython/build/test_python_50750æ', "[Errno 2] No such file or directory: '/home/dje/cpython-buildarea/3.x.edelsohn-sles-z/build/build/test_python_50750æ'")]