Import google/pybind11k from GitHub (google/pybind11clif#30117).

This update needs corresponding changes in third_party/clif/testing/python/t3_test.py

TGP-tested via child CL: http://tap/OCL:626240839:BASE:626375750:1713541129757:e746a257

Note: Currently codesearch finds matches for `pybind11 native_enum` only in third_party/pybind11 and third_party/clif/pybind11.

This CL fixes 12 PyCLIF-pybind11 TGP failures: b/287289622#comment72

#MIGRATION_3P_PYBIND11__DEFAULT

  - e10cb7ec5d7091a817ed0f6a40f4d9f155c644c5 Fix `native_enum` `__module__` attribute: it needs to be ... by Ralf W. Grosse-Kunstleve <[email protected]>

PiperOrigin-RevId: 626400273

clif/testing/python/t3_test.py

@@ -14,14 +14,16 @@
 
 """Tests for clif.testing.python.t3."""
 
+import pickle
 import sys
 
 from absl.testing import absltest
+from absl.testing import parameterized
 
 from clif.testing.python import t3
 
 
-class T3Test(absltest.TestCase):
+class T3Test(parameterized.TestCase):
 
   def testEnumBasic(self):
     self.assertEqual(t3._Old.TOP1, 1)
@@ -37,12 +39,16 @@ def testEnumBasic(self):
 
   def testEnumModuleName(self):
     # This is necessary for proper pickling.
-    if t3.__pyclif_codegen_mode__ == 'pybind11':
-      self.assertEqual(t3._Old.__module__.__name__, t3.__name__)
-      self.assertEqual(t3._New.__module__.__name__, t3.__name__)
-    else:
-      self.assertEqual(t3._Old.__module__, t3.__name__)
-      self.assertEqual(t3._New.__module__, t3.__name__)
+    self.assertEqual(t3._Old.__module__, t3.__name__)
+    self.assertEqual(t3._New.__module__, t3.__name__)
+
+  @parameterized.parameters(
+      t3._Old.TOP1, t3._Old.TOPn, t3._New.TOP, t3._New.BOTTOM
+  )
+  def testPickleRoundtrip(self, orig):
+    serialized = pickle.dumps(orig)
+    restored = pickle.loads(serialized)
+    self.assertEqual(restored, orig)
 
   def testEnumBases(self):
     old_bases = t3._Old.__bases__