Migrate boxInline tests to new multi-file framework

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

@@ -0,0 +1,33 @@
+// FILE: 1.kt
+
+package test
+
+class A {
+    fun call() = inlineFun2 { stub() }
+
+    internal inline fun inlineFun2(p: () -> Unit): String {
+        p()
+
+        return inlineFun {
+            test()
+        }
+    }
+
+    private fun stub() = "fail"
+
+    private fun test() = "OK"
+
+
+    inline internal fun inlineFun(p: () -> String): String {
+        return p()
+    }
+
+}
+
+// FILE: 2.kt
+
+import test.*
+
+fun box(): String {
+    return A().call()
+}