Feature: use mysql's server language as charset

[croconut]

currently the driver ignores the handshake and sends its own internal default as the charset when charset has not been specified in the options argument

please add, in mysql2's next major version, support for using the mysql 'server language' as the default instead

[sidorares]

hey @croconut can you help me to see how this manifests from a user point if view? Ideally self contained example - docker command + client connection script, "ideally expected" vs actual beavior