Merge boxMultiFile testData into box, delete BoxMultiFile test

compiler/testData/codegen/box/multifileClasses/samePartNameDifferentFacades.kt

@@ -0,0 +1,22 @@
+// WITH_RUNTIME
+// FILE: 1/part.kt
+
+@file:JvmName("Foo")
+@file:JvmMultifileClass
+package test
+
+fun foo(): String = "O"
+
+// FILE: 2/part.kt
+
+@file:JvmName("Bar")
+@file:JvmMultifileClass
+package test
+
+fun bar(): String = "K"
+
+// FILE: box.kt
+
+package test
+
+fun box(): String = foo() + bar()