Migrate boxInline tests to new multi-file framework

compiler/testData/codegen/boxInline/private/effectivePrivate.kt

@@ -0,0 +1,31 @@
+// FILE: 1.kt
+
+package test
+
+class Test {
+    private abstract class Base {
+        protected fun duplicate(s: String) = s + "K"
+
+        protected inline fun doInline(block: () -> String): String {
+            return duplicate(block())
+        }
+    }
+
+    private class Extender: Base() {
+        fun doSomething(): String {
+            return doInline { "O" }
+        }
+    }
+
+    fun run(): String {
+        return Extender().doSomething();
+    }
+}
+
+// FILE: 2.kt
+
+import test.*
+
+fun box() : String {
+    return Test().run()
+}