Migrate boxMultiFile and boxMultifileClass tests to new multi-file tests

AbstractCompileKotlinAgainstMultifileKotlinTest is broken in this commit; will
be fixed later

compiler/testData/codegen/boxMultiFile/accessorForProtectedInvokeVirtual.kt

@@ -0,0 +1,67 @@
+// FILE: 1.kt
+
+import test.A
+import kotlin.test.assertEquals
+
+open class B : A() {
+    fun box(): String {
+        val overriddenMethod: () -> String = {
+            method()
+        }
+        assertEquals("C.method", overriddenMethod())
+
+        val superMethod: () -> String = {
+            super.method()
+        }
+        assertEquals("A.method", superMethod())
+
+        val overriddenPropertyGetter: () -> String = {
+            property
+        }
+        assertEquals("C.property", overriddenPropertyGetter())
+
+        val superPropertyGetter: () -> String = {
+            super.property
+        }
+        assertEquals("A.property", superPropertyGetter())
+
+        val overriddenPropertySetter: () -> Unit = {
+            property = ""
+        }
+        overriddenPropertySetter()
+
+        val superPropertySetter: () -> Unit = {
+            super.property = ""
+        }
+        superPropertySetter()
+
+        assertEquals("C.property;A.property;", state)
+
+        return "OK"
+    }
+}
+
+class C : B() {
+    override fun method() = "C.method"
+    override var property: String
+        get() = "C.property"
+        set(value) { state += "C.property;" }
+}
+
+fun box() = C().box()
+
+// FILE: 2.kt
+
+package test
+
+abstract class A {
+    public var state = ""
+
+    // These implementations should not be called, because they are overridden in C
+
+    protected open fun method(): String = "A.method"
+
+    protected open var property: String
+        get() = "A.property"
+        set(value) { state += "A.property;" }
+}