JVM IR: Mark annotation implementation classes as anonymous

And add tests to ensure that annotation implementation classes are
handled correctly in jvm-abi-gen.

plugins/jvm-abi-gen/testData/content/anonymousAnnotationInstantiation/test.kt

@@ -0,0 +1,7 @@
+package test
+
+annotation class A
+
+class Test {
+    fun anonymousAnnotationInstantiation() = A()
+}