[sprout] Add warning/`@OptIn` option for sprout-generated interfaces

[alancai98]

Add an option to add an @OptIn and/or warning for directly implementing a scribe-generated interface. We can create a warning similar to IonJava's interface for IonReader.

For context, adding additional functions to an interface (e.g. adding a plan node) is a breaking change. Our goal here is to allow for adding new nodes to the ast or plan without causing a breaking change.

Additional Context

• Java version: 11
• PartiQL version: 0.14.5-SNAPSHOT
• Add any other context about the problem here.