tls: improve TLSSocket & Server performance

Limit the number of closures created and functions called
throughout the lifecycle of TLSSocket, Server & connect.

PR-URL: #15575
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Fedor Indutny <[email protected]>

Author: apapirovski