Migrate boxInline tests to new multi-file framework

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

@@ -0,0 +1,22 @@
+// FILE: 1.kt
+
+package test
+
+class IntentionsBundle {
+    companion object {
+        internal inline fun message(): String {
+            return KEY + BUNDLE
+        }
+
+        private const val BUNDLE = "K"
+        protected const val KEY = "O"
+    }
+}
+
+// FILE: 2.kt
+
+import test.*
+
+fun box(): String {
+    return IntentionsBundle.message()
+}