Support equivalent of ssl_mode=VERIFY_CA / disableSslHostnameVerification

Currently it seems both CA verification and hostname verification are guarded being the ssl_verify_server_cert option, so an application cannot verify the CA independently of hostname verification.

So this is a feature request to be able to disable hostname verification while still being able to perform peer certificate verification. This is akin to ssl_mode=VERIFY_CA or perhaps the MariaDB connector/j's disableSslHostnameVerification option. In some environments the subject names on a certificate are not terribly interesting, but we would like the client to verify the server's certificate against some provided CA which seems impossible today when using the MariaDB Connector/C.