net: fix timeouts during long writes

Add updateWriteQueueSize which updates and returns queue size
(net & tls). Make _onTimeout check whether an active write
is ongoing and if so, call _unrefTimer rather than emitting
a timeout event.

Add http & https test that checks whether long-lasting (but
active) writes timeout or can finish writing as expected.

PR-URL: https://github.com/nodejs/node/pull/15791
Fixes: https://github.com/nodejs/node/issues/15082


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>