Clear sockets perform worse than TLS socket in some cases

• Version: v13.0.0-pre
• Platform: Linux tufopad 4.15.0-48-generic #51-Ubuntu SMP Wed Apr 3 08:28:49 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
• Subsystem: net

While writing and performing tests for this issue opened by @alexfernandez and fixed by @jmendeth, I noticed that in some cases, clear connections seem to perform worse than TLS connections, specially after the fix that enhances significantly the performance of the TLS connections. I will patch the existing secure-pair benchmark test to expose the issue.

The performance of clear connections seems to be the same across node versions (I've tested it in node 8, 10 and 13-pre). This means that this issue is not a regression, but an enhancement, and the fix needed is probably very similar to the one that solved the secure-pair performance issue.

Inizia con il test di benchmark secure-pair esistente menzionato nell’issue e confronta i suoi casi clear e TLS; esamina l’issue #20263 e la PR #27861 per la modifica delle prestazioni correlata. Il lavoro è completato quando il benchmark evidenzia il rallentamento dei socket clear e l’implementazione di net è migliorata in modo che le connessioni clear non abbiano più prestazioni inferiori nei casi riportati.