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/signatures.txt

@@ -0,0 +1,11 @@
+@java.lang.annotation.Retention(value=RUNTIME)
+@kotlin.Metadata
+public annotation class test/A {
+    // source: 'test.kt'
+}
+@kotlin.Metadata
+public final class test/Test {
+    // source: 'test.kt'
+    public method <init>(): void
+    public final @org.jetbrains.annotations.NotNull method anonymousAnnotationInstantiation(): test.A
+}