Return Violation Messages from Procedural Constraints

[Mythicaeda]

Currently, constraint violation messages are not returned from procedural constraints. To support this in the backend, the following needs to be done:

1. add an Optional<String> message field to the record gov.nasa.jpl.aerie.constraints.model.Violation.
2. update the method fromProceduralViolations gov.nasa.jpl.aerie.constraints.model.Violation to extract the message from the procedural Violation and put it in this new field
3. update violationP in gov.nasa.jpl.aerie.constraints.json.ConstraintParsers to include this new optional message field