This commit makes `TLSSocket` set the `servername` property on
`SSL_CTX_set_tlsext_servername_callback` so that we could get it
later even if errors happen.
Fixes: https://github.com/nodejs/node/issues/27699
PR-URL: https://github.com/nodejs/node/pull/27759
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
