tls: remove usage of public require('util')

Remove the usage of public require('util'), as described in:
https://github.com/nodejs/node/issues/26546

PR-URL: https://github.com/nodejs/node/pull/26747
Refs: https://github.com/nodejs/node/issues/26546


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>