Migrate boxInline tests to new multi-file framework

compiler/testData/codegen/boxInline/reified/checkCast/kt8043.kt

@@ -0,0 +1,26 @@
+// FILE: 1.kt
+
+package test
+
+inline fun <reified T, reified R>T.castTo(): R = this as R
+
+// FILE: 2.kt
+
+import test.*
+
+fun case1(): Int =
+        null.castTo<Int?, Int>()
+
+fun box(): String {
+    failTypeCast { case1(); return "failTypeCast 9" }
+    return "OK"
+}
+
+inline fun failTypeCast(s: () -> Unit) {
+    try {
+        s()
+    }
+    catch (e: TypeCastException) {
+
+    }
+}