gh-117783: Immortalize objects that use deferred reference counting (#118112)

Deferred reference counting is not fully implemented yet. As a temporary
measure, we immortalize objects that would use deferred reference
counting to avoid multi-threaded scaling bottlenecks.

This is only performed in the free-threaded build once the first
non-main thread is started. Additionally, some tests, including refleak
tests, suppress this behavior.

Lib/test/test_code.py

@@ -141,7 +141,8 @@ except ImportError:
     ctypes = None
 from test.support import (cpython_only,
                           check_impl_detail, requires_debug_ranges,
-                          gc_collect, Py_GIL_DISABLED)
+                          gc_collect, Py_GIL_DISABLED,
+                          suppress_immortalization)
 from test.support.script_helper import assert_python_ok
 from test.support import threading_helper, import_helper
 from test.support.bytecode_helper import instructions_with_positions
@@ -577,6 +578,7 @@ class CodeConstsTest(unittest.TestCase):
 
 class CodeWeakRefTest(unittest.TestCase):
 
+    @suppress_immortalization()
     def test_basic(self):
         # Create a code object in a clean environment so that we know we have
         # the only reference to it left.
@@ -827,6 +829,7 @@ if check_impl_detail(cpython=True) and ctypes is not None:
             self.assertEqual(GetExtra(f.__code__, FREE_INDEX+100,
                               ctypes.c_voidp(100)), 0)
 
+        @suppress_immortalization()
         def test_free_called(self):
             # Verify that the provided free function gets invoked
             # when the code object is cleaned up.
@@ -854,6 +857,7 @@ if check_impl_detail(cpython=True) and ctypes is not None:
             del f
 
         @threading_helper.requires_working_threading()
+        @suppress_immortalization()
         def test_free_different_thread(self):
             # Freeing a code object on a different thread then
             # where the co_extra was set should be safe.