Make a decision whether we should enable `TCP_NODELAY` by default or not

The problem here should be related to Nagle’s algorithm, i.e. the TCP_NODELAY option. On Node.js, it's enabled by default: https://nodejs.org/api/http.html#httpcreateserveroptions-requestlistener On actix-web (actix-http), it's disabled by default (no config). I've tested on your benchmark and confirmed enabling it via actix_tls resolved the latency difference. Maybe we should make it enable by default, but it's a behavior change and should happen on major release. For now, I'm going to add a helper method to enable it easily.

Originally posted by @JohnTitor in #3841