Migrate CompileKotlinAgainstKotlin test to multi-file framework

compiler/testData/compileKotlinAgainstKotlin/enum.kt

@@ -0,0 +1,16 @@
+// FILE: A.kt
+
+package aaa
+
+enum class E {
+    TRIVIAL_ENTRY,
+    SUBCLASS { }
+}
+
+// FILE: B.kt
+
+import aaa.E
+
+fun main(args: Array<String>) {
+    if (E.TRIVIAL_ENTRY == E.SUBCLASS) throw AssertionError()
+}