Test: Refactor test fixtures and add SDK session management tests (#8141)

### What problem does this PR solve?

- Consolidate HTTP API test fixtures using batch operations
(batch_add_chunks, batch_create_chat_assistants)
- Fix fixture initialization order in clear_session_with_chat_assistants
- Add new SDK API test suite for session management
(create/delete/list/update)

### Type of change

- [x] Add test cases
- [x] Refactoring

test/testcases/test_http_api/test_chat_assistant_management/conftest.py

@@ -14,7 +14,7 @@
 #  limitations under the License.
 #
 import pytest
-from common import create_chat_assistant, delete_chat_assistants, list_documents, parse_documents
+from common import batch_create_chat_assistants, delete_chat_assistants, list_documents, parse_documents
 from utils import wait_for
 
 
@@ -37,10 +37,4 @@ def add_chat_assistants_func(request, api_key, add_document):
     dataset_id, document_id = add_document
     parse_documents(api_key, dataset_id, {"document_ids": [document_id]})
     condition(api_key, dataset_id)
-
-    chat_assistant_ids = []
-    for i in range(5):
-        res = create_chat_assistant(api_key, {"name": f"test_chat_assistant_{i}", "dataset_ids": [dataset_id]})
-        chat_assistant_ids.append(res["data"]["id"])
-
-    return dataset_id, document_id, chat_assistant_ids
+    return dataset_id, document_id, batch_create_chat_assistants(api_key, 5)