pool: process all events as soon as possible

before we were only processing one event per frame. This ensured that
not too much time is spent processing events in a single frame.
Unfortunately since we don't have persistent frame rendering, this is
not reliable.

We can look into limiting the number of events processed per frame if
message processing gets heavy.

src/app.rs

@@ -119,7 +119,7 @@ fn try_process_event(damus: &mut Damus, ctx: &egui::Context) {
     damus.pool.keepalive_ping();
 
     // pool stuff
-    if let Some(ev) = damus.pool.try_recv() {
+    while let Some(ev) = damus.pool.try_recv() {
         let relay = ev.relay.to_owned();
 
         match ev.event {