Check that the default signature type is allowed

Check that the default signature type is allowed

TLS < 1.2 has fixed signature algorithms: MD5+SHA1 for RSA and SHA1 for the
others. TLS 1.2 sends a list of supported ciphers, but allows not sending
it in which case SHA1 is used. TLS 1.3 makes sending the list mandatory.

When we didn't receive a list from the client, we always used the
defaults without checking that they are allowed by the configuration.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
GH: #10784