enable v1 endpoint on agent for efficient payload scenario (#5569)

Co-authored-by: Charles de Beauchesne <charles.debeauchesne@datadoghq.com>

Author: ajgajg1134

utils/_context/_scenarios/__init__.py

@@ -541,6 +541,9 @@ class _Scenarios:
             "DD_TRACE_SAMPLE_RATE": "1.0",
             "DD_TRACE_V1_PAYLOAD_FORMAT_ENABLED": "true",
         },
+        agent_env={
+            "DD_APM_ENABLE_V1_TRACE_ENDPOINT": "true",
+        },
         backend_interface_timeout=5,
         doc="End-to-end testing scenario focused on efficient payload handling and v1 trace format validation",
     )