[FIR] Reorganize modules of raw fir builders

compiler/fir/raw-fir/psi2fir/testData/rawBuilder/declarations/nestedClass.kt

@@ -0,0 +1,7 @@
+abstract class Base(val s: String)
+
+class Outer {
+    class Derived(s: String) : Base(s)
+
+    object Obj : Base("")
+}