Support passing custom annotations to generated code

With the work in PR https://github.com/mapstruct/mapstruct/pull/2792 being done for https://github.com/mapstruct/mapstruct/issues/1574 it would be good to provide some support for the new API in the IntelliJ plugin as well.

Some things that we should do:

• Auto completion support for AnnotateWith.Element#name and error when name does not exist in target enum.
• Smart auto completion for AnnotateWith.Element#classes (pick the class type based on the one in the annotation
• Auto completion for AnnotateWith.Element#enums and error when enum value does not exist
• Annotation cannot annotated the generated class / method (it doesn't have the right target element type)
• Error when more than one value type is provided, eg. shorts() and strings()
• Error when duplicated AnnotateWith.Element#name (more than one having the same name
• Error when value does not match target annotation value type
• Error when using array value, but target value is not an array

Beginne damit, PR #2792 und Issue #1574 zu lesen, um die neue AnnotateWith API zu verstehen, und untersuche anschließend die bestehende Unterstützung des IntelliJ-Plugins für generierte Annotationen. Als erledigt gilt die Implementierung und Validierung der aufgeführten Vervollständigungs- und Fehlerprüfungen, einschließlich Zielkompatibilität, doppelter Namen, Werttypen und Arrays.