tls: fix getEphemeralKeyInfo to support X25519

`EVP_PKEY_EC` only covers ANSI X9.62 curves not IETF ones(curve25519
and curve448). This fixes to add support of X25519 in
`tlsSocket.getEphemeralKeyInfo()`.
X448 should be added in the future upgrade to OpenSSL-1.1.1.

PR-URL: https://github.com/nodejs/node/pull/20273
Fixes: https://github.com/nodejs/node/issues/20262


Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>