Migrate boxInline tests to new multi-file framework

compiler/testData/codegen/boxInline/syntheticAccessors/superProperty.kt

@@ -0,0 +1,24 @@
+// FILE: 1.kt
+
+package test
+
+open class A {
+    open val test = "OK"
+}
+
+object X : A() {
+    override val test: String
+        get() = "fail"
+
+    inline fun doTest(): String {
+        return super.test
+    }
+}
+
+// FILE: 2.kt
+
+import test.*
+
+fun box(): String {
+    return X.doTest()
+}