adds tls sni support to mysql2

[mikemackintosh]

This pull request introduces support for specifying a TLS SNI (Server Name Indication) name during MySQL client connections. This enhancement allows users to set a custom SNI hostname for TLS connections, improving flexibility and compatibility with certain server configurations.

Enhancements to TLS Configuration:

• Updated the rb_mysql_connect function in ext/mysql2/client.c to accept an additional parameter, tls_sni_name, and use it to set the TLS SNI server name via the MYSQL_OPT_TLS_SNI_SERVERNAME option in the MySQL client library. [1] [2]
• Modified the init_mysql2_client function in ext/mysql2/client.c to reflect the updated rb_mysql_connect method signature, increasing the number of expected arguments from 8 to 9.

Updates to Ruby Client Initialization:

• Added support for the :tls_sni_name option in the initialize method of lib/mysql2/client.rb, allowing users to specify the SNI name when creating a MySQL client instance.
• Ensured the tls_sni_name value is converted to a string if provided, and passed it as an argument to the updated connect method.