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/proxy.rs

@@ -132,16 +132,14 @@ pub async fn task_main(
                 Err(e) => {
                     // todo: log and push to ctx the error kind
                     ctx.set_error_kind(e.get_error_kind());
-                    ctx.log();
                     error!(parent: &span, "per-client task finished with an error: {e:#}");
                 }
                 Ok(None) => {
                     ctx.set_success();
-                    ctx.log();
                 }
                 Ok(Some(p)) => {
                     ctx.set_success();
-                    ctx.log();
+                    ctx.log_connect();
                     match p.proxy_pass().instrument(span.clone()).await {
                         Ok(()) => {}
                         Err(e) => {