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/kotlinSignature/propagation/parameter/InheritVararg.fir.txt

@@ -1,2 +1,12 @@
 public abstract interface InheritVararg : R|kotlin/Any| {
+    public abstract interface Sub : R|test/InheritVararg.Super| {
+        public abstract fun foo(p: R|ft<kotlin/Array<ft<kotlin/String, kotlin/String?>>, kotlin/Array<out ft<kotlin/String, kotlin/String?>>?>|): R|kotlin/Unit|
+
+    }
+    public abstract interface Super : R|kotlin/Any| {
+        public abstract fun foo(vararg p: R|ft<kotlin/Array<ft<kotlin/String, kotlin/String?>>, kotlin/Array<out ft<kotlin/String, kotlin/String?>>?>|): R|kotlin/Unit|
+
+        public abstract fun dummy(): R|kotlin/Unit|
+
+    }
 }