feat(strategy-state): persist instance-scoped slot maps

tests/application/test_slots_handler.py

@@ -43,6 +43,8 @@ def _req(filter=None, spy=False):
         payload["filter"] = filter
     if spy:
         payload["spy"] = True
+    else:
+        payload["strategy_instance_id"] = "test-instance"
     return RpcRequest(payload=payload, correlation_id="test-corr")