refactor: modify ExperimentManager to take config instead of agent_config and call before session creation (#10001)

Co-authored-by: openhands <openhands@all-hands.dev>

openhands/experiments/experiment_manager.py

@@ -1,5 +1,7 @@
 import os
 
+from openhands.core.config.openhands_config import OpenHandsConfig
+from openhands.core.logger import openhands_logger as logger
 from openhands.server.session.conversation_init_data import ConversationInitData
 from openhands.utils.import_utils import get_impl
 
@@ -11,6 +13,15 @@ class ExperimentManager:
     ) -> ConversationInitData:
         return conversation_settings
 
+    @staticmethod
+    def run_config_variant_test(
+        user_id: str, conversation_id: str, config: OpenHandsConfig
+    ) -> OpenHandsConfig:
+        logger.debug(
+            f'Running agent config variant test for user_id={user_id}, conversation_id={conversation_id}'
+        )
+        return config
+
 
 experiment_manager_cls = os.environ.get(
     'OPENHANDS_EXPERIMENT_MANAGER_CLS',