【Feature】add fd plugins && rm model_classes (#3123)

* add fd plugins && rm model_classed

* fix reviews

* add docs

* fix

* fix unitest ci

fastdeploy/plugins/__init__.py

@@ -0,0 +1,20 @@
+"""
+# Copyright (c) 2025  PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+
+from .model_register import load_model_register_plugins
+from .model_runner import load_model_runner_plugins
+
+__all__ = ["load_model_register_plugins", "load_model_runner_plugins"]