Function spawn_rpc_proxy_rejecting_method_after_when_enabled 

pub async fn spawn_rpc_proxy_rejecting_method_after_when_enabled(
    endpoint: String,
    method: &'static str,
    successful_calls: usize,
) -> (String, Arc<AtomicBool>)

Spawns an RPC proxy that forwards successful_calls requests to method, then rejects later requests while the returned switch is enabled.