Optionally disable hostname verification for SslMode.TUNNEL

[shubha-rajan]

Hi, we're working on supporting the MariaDB r2dbc driver in the Cloud SQL Java Connector. Cloud SQL certificates provide the instance name as the Common Name instead of a domain, which means that verifying hostnames will fail. Some examples:

• https://stackoverflow.com/questions/72214865/set-up-google-cloud-certificates-for-postgresql-database-hostname-mismatch
• https://stackoverflow.com/questions/61334993/cannot-tls-connect-to-gcp-cloud-sqlmysql-using-python3
• https://stackoverflow.com/questions/33878356/certificate-validation-on-cloud-sql

Currently, the MariaDB driver forces hostname verification when using SslMode.TUNNEL. I have a patch pull request in which I added the option to disable host verification for SSL Tunneling which I will link here.