Function execute_handler 

pub fn execute_handler(
    handler: BuiltinHandler,
    state: &BuiltinHandlerState,
    request_id: &str,
    config: Option<Arc<Config>>,
    upstreams: Option<UpstreamHealthSnapshot>,
    cache_stats: Option<Arc<HttpCacheStats>>,
    cache_purge: Option<CachePurgeRequest>,
    cache_manager: Option<&Arc<CacheManager>>,
) -> Response<Full<Bytes>>

Execute a builtin handler