crypto: prevent Sign::SignFinal from crashing

The validation logic could be tricked into assuming an option was
valid using malicious getters, leading to an invalid value being
passed to the C++ layer, thus crashing the process.

PR-URL: https://github.com/nodejs/node/pull/21815


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>