Signer ignores PSS

On both `windows` and `darwin`, using the `Signer` of an `Identity` object as a private key of a TLS certificate doesn't work against a server that requires TLS v1.3.
In this case, a GO TLS server, for example, returns an "error decrypting message" error due to missing `0xbc` at the end of the signature during the handshake. The reason for this is not using the padding scheme when signing the digest.