Move some tests from boxWithStdlib/ to box/

Move those tests which do not require neither stdlib nor reflect

compiler/testData/codegen/box/dataClasses/toString/unitComponent.kt

@@ -0,0 +1,6 @@
+data class A(val x: Unit)
+
+fun box(): String {
+    val a = A(Unit)
+    return if ("$a" == "A(x=kotlin.Unit)") "OK" else "$a"
+}