Add codegen box test templates for identifiers

compiler/tests-spec/testData/codegen/box/templates/identifiers/packageSimple.kt

@@ -0,0 +1,9 @@
+<!DIRECTIVES("HELPERS: REFLECT")!>
+
+package <!ELEMENT(1)!>
+
+fun box(): String? {
+    if (!checkPackageName("<!ELEMENT_VALIDATION(1)!>.<!CLASS_OF_FILE!>", "<!ELEMENT_VALIDATION(1)!>")) return null
+
+    return "OK"
+}