Add tree_merge for law parsers, significantly outperforming hierarchical_merge (#10202)

### What problem does this PR solve?
Add tree_merge for law parsers, significantly outperforming
hierarchical_merge, solved: #8637
1. Add tree_merge for law parsers, include build_tree and get_tree by
dfs.
2. add Copyright statement for helath_utils
### Type of change

- [x] Documentation Update
- [x] Performance Improvement

api/utils/health_utils.py

@@ -1,3 +1,20 @@
+#
+#  Copyright 2025 The InfiniFlow 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 timeit import default_timer as timer
 
 from api import settings