The problem was that we tried to generate an `$annotations` method for a
property declared in an annotation class. That method is final and has a
body, which is not allowed in annotation classes. Now we're generating
this method in the separate `$DefaultImpls` class as for properties in
interfaces.
Note that the added test still doesn't find any annotations because the
proper support is needed in reflection (KT-22463). Currently it only
checks that no VerifyError happens.