[proxy] replace the batch cancellation queue, shorten the TTL for cancel keys (#11943)

See #11942 

Idea: 
* if connections are short lived, they can get enqueued and then also
remove themselves later if they never made it to redis. This reduces the
load on the queue.
* short lived connections (<10m, most?) will only issue 1 command, we
remove the delete command and rely on ttl.
* we can enqueue as many commands as we want, as we can always cancel
the enqueue, thanks to the ~~intrusive linked lists~~ `BTreeMap`.

proxy/src/binary/local_proxy.rs

@@ -201,7 +201,7 @@ pub async fn run() -> anyhow::Result<()> {
         auth_backend,
         http_listener,
         shutdown.clone(),
-        Arc::new(CancellationHandler::new(&config.connect_to_compute, None)),
+        Arc::new(CancellationHandler::new(&config.connect_to_compute)),
         endpoint_rate_limiter,
     );