FIR: dump nested classes in loadJava tests

Because those test are single Java files, many of them use a top-level
class as a container for multiple classes to be tested. Such tests do
almost nothing if those nested classes aren't handled.

compiler/testData/loadJava/compiledJava/annotations/StringConstantInParam.fir.txt

@@ -1,4 +1,12 @@
 public abstract interface StringConstantInParam : R|kotlin/Any| {
     public final static field HEL: R|ft<kotlin/String, kotlin/String?>| = String(hel)
 
+    public final annotation class Anno : R|kotlin/Annotation| {
+        public constructor(value: R|kotlin/String|): R|test/StringConstantInParam.Anno|
+
+    }
+    @R|test/StringConstantInParam.Anno|(String(hello)) public open class Class : R|kotlin/Any| {
+        public constructor(): R|test/StringConstantInParam.Class|
+
+    }
 }