Migrate boxInline tests to new multi-file framework

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

@@ -0,0 +1,25 @@
+// FILE: 1.kt
+
+@file:kotlin.jvm.JvmMultifileClass
+@file:kotlin.jvm.JvmName("TestKt")
+package test
+
+private val prop = "O"
+
+private fun test() = "K"
+
+inline internal fun inlineFun(): String {
+    return prop + test()
+}
+
+class A () {
+    fun call() = inlineFun()
+}
+
+// FILE: 2.kt
+
+import test.*
+
+fun box(): String {
+    return A().call();
+}