Refactor: migrate chunk retrieval_test and knowledge_graph to REST API endpoints (#14402)

### 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` |

web/src/utils/api.ts

@@ -66,6 +66,8 @@ export default {
   getKbDetail: (datasetId: string) => `${restAPIv1}/datasets/${datasetId}`,
   getKnowledgeGraph: (knowledgeId: string) =>
     `${restAPIv1}/datasets/${knowledgeId}/graph/search`,
+  knowledgeGraph: (datasetId: string) =>
+    `${restAPIv1}/datasets/${datasetId}/graph`,
   deleteKnowledgeGraph: (knowledgeId: string) =>
     `${restAPIv1}/datasets/${knowledgeId}/graph`,
   getMeta: `${restAPIv1}/datasets/metadata/flattened`,
@@ -107,8 +109,8 @@ export default {
     `${restAPIv1}/datasets/${datasetId}/documents/${documentId}/chunks`,
   chunkDetail: (datasetId: string, documentId: string, chunkId: string) =>
     `${restAPIv1}/datasets/${datasetId}/documents/${documentId}/chunks/${chunkId}`,
-  retrievalTest: `${webAPI}/chunk/retrieval_test`,
-  knowledgeGraph: `${webAPI}/chunk/knowledge_graph`,
+  retrievalTest: (datasetId: string) =>
+    `${restAPIv1}/datasets/${datasetId}/search`,
 
   // document
   getDocumentList: (datasetId: string) =>