Class is an annotation iff it is annotated by kotlin.annotation.annotation, or is kotlin.annotation.annotation itself.

JetClassOrObject.isAnnotation() is no more in use during resolve. Additional test.

compiler/testData/diagnostics/tests/annotations/AnnotationIdentifier.kt

@@ -0,0 +1,25 @@
+// FILE: a.kt
+
+<!NOT_AN_ANNOTATION_CLASS!>annotation<!> class annotation
+
+// FILE: test/b.kt
+
+package test
+
+<!NOT_AN_ANNOTATION_CLASS!>test.annotation<!> class annotation
+
+kotlin.annotation.annotation class realAnnotation
+
+realAnnotation class My
+
+// FILE: other/c.kt
+
+package other
+
+annotation class My
+
+<!NOT_AN_ANNOTATION_CLASS!>test.annotation<!> class Your
+
+kotlin.annotation.annotation class His
+
+My class Our