### 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
### What problem does this PR solve?
Support server health check. Solved issue: #10106
### Type of change
- [x] New Feature (non-breaking change which adds functionality)