Allow xbase expressions in annotation parameter value

[abelhegedus]

This would be nice in several use cases when some basic manipulation of the match values is needed.

The idea was conceived when thinking about creating invertable derived features but a similar usecase occurs in the message of validation annotation, and maybe the observable values in databinding.

Example:

@DerivedFeature(invert = {Target.id}, invertFeature="targetId")
@Constraint(location = "Source",
    message = {"Source " + Source.name + " connected to " + Target.name + "},
    severity = "info")
pattern softLink(Source, Target) {
  Source.targetId(Source, ID);
  Target.id(Target, ID);
}

[bergmanngabor]

I would also list OrderBy as a separate future use case - although if we ever add support for it in EMF-IncQuery, we could also consider a dedicated language element in this case. Anyways, in Viatra, we would have made good use of expressions in the annotation.

[ujhelyiz]

Migrated to https://bugs.eclipse.org/bugs/show_bug.cgi?id=398816