gh-116510: Fix crash due to shared immortal interned strings.

[nascheme]

Fix a crash caused by immortal interned strings being shared between
sub-interpreters that use basic single-phase init. In that case, the string
can be used by an interpreter that outlives the interpreter that created and
interned it. For interpreters that share obmalloc state, also share the
interned dict with the main interpreter.

• Issue: CPython 3.12 embedded in WeeChat causes segfault on subsequent calls to Py_EndInterpreter #116510

[miss-islington-app]

Thanks @nascheme for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[bedevere-app]

GH-124648 is a backport of this pull request to the 3.13 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot iOS ARM64 Simulator 3.x has failed when building commit 98b2ed7.

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/1380/builds/1423) and take a look at the build logs.
4. Check if the failure is related to this commit (98b2ed7) 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/1380/builds/1423

Failed tests:

• test_support

Failed subtests:

• test_fd_count - test.test_support.TestSupport.test_fd_count

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

==

Click to see traceback logs

Traceback (most recent call last):
  File "/Users/buildbot/Library/Developer/XCTestDevices/D9F34191-E74B-4D29-B721-2C5A66CE9BF9/data/Containers/Bundle/Application/C6972B3B-1B34-4FF9-A4EE-30CA8E98F224/iOSTestbed.app/python/lib/python3.14/test/test_support.py", line 565, in test_fd_count
    self.assertEqual(more - start, 1)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
AssertionError: 0 != 1

[mhsmith]

@freakboy3742: It might be a good idea to skip this test on iOS for the same reason as WASM: "The platform starts and stops background threads that use fds". I haven't seen this failure on Android yet, but I did have to skip a similar one in test_fd_leak in test_os.py.

[freakboy3742]

@mhsmith Agreed; see #124683