Function explain_subscribe_inner 

async fn explain_subscribe_inner(
    session: &Session,
    catalog: &Catalog,
    df_meta: DataflowMetainfo,
    explain_ctx: ExplainPlanContext,
    sink_id: GlobalId,
    cluster_id: ComputeInstanceId,
    features: &OptimizerFeatures,
) -> Result<Vec<Row>, AdapterError>

Renders the rows of an EXPLAIN ... SUBSCRIBE from its optimizer trace.

features are the optimizer features the SUBSCRIBE was optimized with.