Remember Cloud SQL Proxy alternate port

The Cloud SQL Proxy integration in DataGrip is very nice and makes the process of setting up these connections much smoother.

I understand that [auto-resolving port conflicts is a known issue](https://cloud.google.com/code/docs/intellij/connect-sql-database#set_a_different_port_to_connect_to_several_databases) and likely not something the plugin wants to get into the business of solving.

However, it would be nice to have a settings panel entry to specify an alternate default port. Even a global setting that isn't instance-specific would be helpful. Without this, you have to remember and manually respecify the alternate port each time you open a connection.

While the documentation entry talks about this as an issue with multiple connections to different instances, it's also a persistent and unresolvable conflict if you have a local copy of the target database running on the engine's default port.