Use a single long-lived RPC connection when authenticated

The prior system spawned a new connection per request to enable parallelism,
yet kept hitting hyper::IncompleteMessages I couldn't track down. This
attempts to resolve those by a long-lived socket.

Halves the amount of requests per-authenticated RPC call, and accordingly is
likely still better overall.

I don't believe this is resolved yet but this is still worth pushing.

processor/src/main.rs

@@ -650,7 +650,7 @@ async fn main() {
     #[cfg(feature = "bitcoin")]
     NetworkId::Bitcoin => run(db, Bitcoin::new(url).await, coordinator).await,
     #[cfg(feature = "monero")]
-    NetworkId::Monero => run(db, Monero::new(url), coordinator).await,
+    NetworkId::Monero => run(db, Monero::new(url).await, coordinator).await,
     _ => panic!("spawning a processor for an unsupported network"),
   }
 }

processor/src/networks/monero.rs

@@ -191,8 +191,8 @@ fn map_rpc_err(err: RpcError) -> NetworkError {
 }
 
 impl Monero {
-  pub fn new(url: String) -> Monero {
-    Monero { rpc: HttpRpc::new(url).unwrap() }
+  pub async fn new(url: String) -> Monero {
+    Monero { rpc: HttpRpc::new(url).await.unwrap() }
   }
 
   fn view_pair(spend: EdwardsPoint) -> ViewPair {

processor/src/tests/literal/mod.rs

@@ -114,13 +114,15 @@ mod monero {
 
   async fn monero(ops: &DockerOperations) -> Monero {
     let handle = ops.handle("serai-dev-monero").host_port(18081).unwrap();
-    let monero = Monero::new(format!("http://serai:seraidex@{}:{}", handle.0, handle.1));
+    let url = format!("http://serai:seraidex@{}:{}", handle.0, handle.1);
     for _ in 0 .. 60 {
-      if monero.get_latest_block_number().await.is_ok() {
+      if monero_serai::rpc::HttpRpc::new(url.clone()).await.is_ok() {
         break;
       }
       tokio::time::sleep(core::time::Duration::from_secs(1)).await;
     }
+
+    let monero = Monero::new(url).await;
     while monero.get_latest_block_number().await.unwrap() < 150 {
       monero.mine_block().await;
     }