feat: Put request rate limit at application server (#3857)

* feat: Put request rate limit at application server

This PR contains implementation for a blanket rate limiter at
application server level. Currently the allowed throughput is set high
only to be changed later as per the actual data gathered.

* Simplify implementation

1. Remove shutdown handler to purge rate limiter keys
2. Have separate keys for default and custom(route-based) rate limiters
3. Do not kill default rate limiter because it is not needed anymore due
   to (2) above

* Set 60s as default for rate limiting window

* Fix env types

server/index.ts

@@ -122,6 +122,7 @@ async function start(id: number, disconnect: () => void) {
       }`
     );
   });
+
   server.listen(normalizedPortFlag || env.PORT || "3000");
   process.once("SIGTERM", shutdown);
   process.once("SIGINT", shutdown);