Annotations: Only instantiate annotations by migrator if needed

* Refactor the AnnotationValueService to add a check for the need to
  instantiate annotations to the public API. The performance impact is
  neglible due to caching support in the service at two relevant places.
* Use the provided method to check if a "migration" for adding
  annotations is actually needed. This avoids indicating the need for
  migration for every model as in the previous implementation.

Issue-Ref: 3838
Issue-Url: https://af3-developer.fortiss.org/issues/3838


Signed-off-by: Alexander Diewald <diewald@fortiss.org>