gh-99113: Add PyInterpreterConfig.own_gil (gh-104204)

We also add PyInterpreterState.ceval.own_gil to record if the interpreter actually has its own GIL.

Note that for now we don't actually respect own_gil; all interpreters still share the one GIL.  However, PyInterpreterState.ceval.own_gil does reflect PyInterpreterConfig.own_gil.  That lie is a temporary one that we will fix when the GIL really becomes per-interpreter.

Lib/test/test_threading.py

@@ -1349,6 +1349,7 @@ class SubinterpThreadingTests(BaseTestCase):
                 allow_threads={allowed},
                 allow_daemon_threads={daemon_allowed},
                 check_multi_interp_extensions=False,
+                own_gil=False,
             )
             """)
         with test.support.SuppressCrashReport():