Make Wave more resilient to unstable networks

[mturoci]

As of today, Wave requires a stable websocket connection. However, some environments cut websocket connections on purpose to save on resources which results in subpar UX.

The goal of this issue is to handle underlying reconnects in the background so that users can use the app undisturbed without notice.

• Requires UI change to only rerender the page if reconnect failed. First reconnect should be with zero backoff (immediate).
• Server needs to allow resumability - distinguish between reconnects and new connects.

cc @codyharris-h2o-ai @mmalohlava