Refa: Move HTTP API tests to top-level test directory (#8042)

### What problem does this PR solve?

Move test cases only - CI still runs tests under sdk/python

### Type of change

- [x] Refactoring

test/testcases/test_http_api/test_session_management/conftest.py

@@ -0,0 +1,53 @@
+#
+#  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.
+#
+import pytest
+from common import create_session_with_chat_assistant, delete_session_with_chat_assistants
+
+
+@pytest.fixture(scope="class")
+def add_sessions_with_chat_assistant(request, api_key, add_chat_assistants):
+    _, _, chat_assistant_ids = add_chat_assistants
+
+    def cleanup():
+        for chat_assistant_id in chat_assistant_ids:
+            delete_session_with_chat_assistants(api_key, chat_assistant_id)
+
+    request.addfinalizer(cleanup)
+
+    session_ids = []
+    for i in range(5):
+        res = create_session_with_chat_assistant(api_key, chat_assistant_ids[0], {"name": f"session_with_chat_assistant_{i}"})
+        session_ids.append(res["data"]["id"])
+
+    return chat_assistant_ids[0], session_ids
+
+
+@pytest.fixture(scope="function")
+def add_sessions_with_chat_assistant_func(request, api_key, add_chat_assistants):
+    _, _, chat_assistant_ids = add_chat_assistants
+
+    def cleanup():
+        for chat_assistant_id in chat_assistant_ids:
+            delete_session_with_chat_assistants(api_key, chat_assistant_id)
+
+    request.addfinalizer(cleanup)
+
+    session_ids = []
+    for i in range(5):
+        res = create_session_with_chat_assistant(api_key, chat_assistant_ids[0], {"name": f"session_with_chat_assistant_{i}"})
+        session_ids.append(res["data"]["id"])
+
+    return chat_assistant_ids[0], session_ids