### What problem does this PR solve?
## Summary
Migrate two web API endpoints to REST-style HTTP API endpoints,
following the pattern established in #14222:
| Old Endpoint | New Endpoint |
|---|---|
| `POST /v1/chunk/retrieval_test` | `POST
/api/v1/datasets/<dataset_id>/search` |
| `GET /v1/chunk/knowledge_graph` | `GET
/api/v1/datasets/<dataset_id>/graph` |
### What problem does this PR solve?
1. Split dataset api to gateway and service, and modify web UI to use
restful http api.
2. Old KB releated APIs are commented.
### Type of change
- [x] Refactoring
---------
Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>
### What problem does this PR solve?
1. Split dataset api to gateway and service, and modify web UI to use
restful http api.
2. Old KB releated APIs are commented.
### Type of change
- [x] Refactoring
### What problem does this PR solve?
1. Split dataset api to gateway and service, and modify web UI to use
restful http api.
2. Old KB releated APIs are commented.
### Type of change
- [x] Refactoring