Remove the custom error / rejection handling for routes in Delta

[imsdu]

Motivation
This was the case because back when we were using Monix BIO not all errors were exceptions.
Now that they all are we can rely on the ExceptionHandler and RejectionHandler provided by akka

Acceptance criteria

1. There is no impact on error/rejection handling
2. Code should be simplified

This section should be about results in domain terms, not implementation details.

Implementation notes

• Every plugin will have to register its ExceptionHandler (it should be easy with Distage)
• ResponseToJsonLd should only take care of the success path