proxy: Create disconnect events (#7535)

## Problem

It's not possible to get the duration of the session from proxy events.

## Summary of changes

* Added a separate events folder in s3, to record disconnect events. 
* Disconnect events are exactly the same as normal events, but also have
`disconnect_timestamp` field not empty.
* @oruen suggested to fill it with the same information as the original
events to avoid potentially heavy joins.

proxy/src/bin/pg_sni_router.rs

@@ -279,7 +279,7 @@ async fn handle_client(
 
     // doesn't yet matter as pg-sni-router doesn't report analytics logs
     ctx.set_success();
-    ctx.log();
+    ctx.log_connect();
 
     // Starting from here we only proxy the client's traffic.
     info!("performing the proxy pass...");