[Model] Add native MAGI-2 Preview diffusion support (#5918)

Signed-off-by: Hongsheng Liu <liuhongsheng4@huawei.com>
Signed-off-by: hsliuustc0106 <liuhongsheng4@huawei.com>

tests/diffusion/attention/test_attention_config.py

@@ -907,6 +907,7 @@ class TestAttentionInitUsesCurrentDiffusionConfig:
                 forward=lambda *args: pytest.fail("unexpected SDPA fallback"),
             ),
             _assert_metadata_compatible=lambda metadata: None,
+            _has_custom_attention=False,
             _scheduler_paged_kv=False,
             paged_kv_cache_role=None,
         )