crypto: add support for PEM-level encryption

This adds support for PEM-level encryption as defined in RFC 1421.
PEM-level encryption is intentionally unsupported for PKCS#8 private
keys since PKCS#8 defines a newer encryption format.

PR-URL: https://github.com/nodejs/node/pull/23151
Refs: https://github.com/nodejs/node/pull/22660


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>