crypto: estimate kExternalSize

Based on a build of OpenSSL 1.1.0f.

The exact sizes are not particularly important (the original value was
missing all the objects hanging off anyway), only that V8 garbage
collector be aware that there is some memory usage beyond the sockets
themselves.

PR-URL: https://github.com/nodejs/node/pull/16130
Backport-PR-URL: https://github.com/nodejs/node/pull/18622


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rod Vagg <rod@vagg.org>