Add SslCa connection string option

[bgrainger]

In Connector/NET 8.0, an SslCa connection string option was added. https://dev.mysql.com/doc/connector-net/en/connector-net-8-0-connection-options.html:

SslCa , Ssl-Ca
Default: null

Based on the type of certificates being used, this option either specifies the path to a certificate file in PKCS #12 format (.pfx) or the path to a file in PEM format (.pem) that contains a list of trusted SSL certificate authorities (CA).

We already support loading the server's certificate in PEM format with the CACertificateFile option.

For compatibility, SslCa and Ssl-Ca should be added as synonyms.

[bgrainger]

In Connector/NET, SslCa (server CA key) and CertificateFile (client SSL certificate) are aliases of each other in the connection string.

From https://dev.mysql.com/doc/connector-net/en/connector-net-8-0-connection-options.html:

Based on the type of certificates being used, this option either specifies the path to a certificate file in PKCS #12 format (.pfx) or the path to a file in PEM format (.pem) that contains a list of trusted SSL certificate authorities (CA).

This means that with Connector/NET, you can have a connection string in the format CertificateFile=server-ca.pem;SslKey=client-key.pem;SslCert=client-cert.pem and it will use server-ca.pem to verify the server's certificate.

This is incompatible with MySqlConnector, which always uses CertificateFile for the client certificate and allows it to be used in combination with CACertificateFile (aka SslCa) to specify the server's CA key.

Fortunately, all the Oracle documentation gives the option name as SslCa in their examples, so migration from their recommended syntax will work fine.

[bgrainger]

Filed an Oracle bug stating why I think their implementation is flawed: https://bugs.mysql.com/bug.php?id=95526