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

まず PR #2792 と issue #1574 を読んで新しい AnnotateWith API を理解し、次に IntelliJ プラグインに既にある生成アノテーションのサポートを調べてください。完了条件は、対象互換性、重複した名前、値の型、配列を含む、列挙された補完およびエラーチェックを実装して検証することです。