Function process_response_and_observe_metrics 

pub fn process_response_and_observe_metrics<T>(
    annotated: &Annotated<T>,
    response_collector: &mut ResponseMetricCollector,
    http_queue_guard: &mut Option<HttpQueueGuard>,
)

Process streaming metrics for annotated responses

This function handles metrics collection and http_queue_guard management for streaming responses. It observes the current output sequence length, drops the http_queue_guard on the first token, and records response metrics.