pki_crypto: Support Ed25519 keys in PEM files
This adds support for Ed25519 keys from files in PEM format when using
OpenSSL with Ed25519 support. The default encoding for the PEM file is
expected to be PKCS#8. Encrypted files are supported.
For the lack of an API, it is not possible to export keys in PEM format,
only in OpenSSH format.
Signed-off-by: Anderson Toshiyuki Sasaki <email@example.com>
Reviewed-by: Jakub Jelen <firstname.lastname@example.org>