Fix LayerNorm Problem Release2.1 (#33534)

* Eliminate numerical differences of LayerNorm; fix LayerNorm Nan Bug while large data input

* fix bug while large shape of data input

python/paddle/fluid/tests/unittests/test_layer_norm_op_v2.py

@@ -51,6 +51,7 @@ class TestDygraphLayerNormv2(unittest.TestCase):
             self.assertTrue(np.allclose(y1, y2))
 
     def test_static(self):
+        paddle.enable_static()
         places = [fluid.CPUPlace()]
         if core.is_compiled_with_cuda() and core.op_support_gpu("layer_norm"):
             places.append(fluid.CUDAPlace(0))