Adapt CompileKotlinAgainstKotlin test to black box format

Rename/remove some obsolete test cases

compiler/testData/compileKotlinAgainstKotlin/nestedClass.kt

@@ -4,15 +4,12 @@ package aaa
 
 class A {
     class O {
-      val s = "OK"
+        val s = "OK"
     }
 }
 
 // FILE: B.kt
 
-fun main(args: Array<String>) {
-    val str = aaa.A.O().s
-    if (str != "OK") {
-        throw Exception()
-    }
+fun box(): String {
+    return aaa.A.O().s
 }