Minor, move irText tests on data classes to a subdirectory

compiler/testData/ir/irText/classes/dataClasses/dataClassesGeneric.kt

@@ -0,0 +1,7 @@
+data class Test1<T>(val x: T)
+
+data class Test2<T : Number>(val x: T)
+
+data class Test3<T>(val x: List<T>)
+
+data class Test4(val x: List<String>)