Snowflake Connector: Add support for `privateKey` authentication property

[parthshyara]

The Trino Snowflake connector currently does not support using the privateKey property that the Snowflake JDBC driver exposes for key-pair authentication. According to the Snowflake documentation, this property allows passing a private key directly in the connection properties:
https://docs.snowflake.com/en/developer-guide/jdbc/jdbc-configure#privatekey-property-in-connection-properties

Right now, Trino only supports passing key-related parameters through the JDBC URL. That approach requires providing a file path and password, which can introduce security risks and add operational overhead. Managing file paths is particularly difficult in containerized or cloud-native environments.

Supporting the privateKey property directly would be both safer and more convenient. It removes the need to reference external files and instead allows secure configuration as part of the catalog itself. This makes key-pair authentication much easier to adopt while aligning with best practices for passwordless connections.

In our use case, we are also leveraging dynamic catalog creation. Having support for the privateKey property at the catalog level makes this workflow much simpler and avoids the complexity of file-based approaches, which are harder to manage dynamically.