Add codegen box test templates for identifiers

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

@@ -0,0 +1,27 @@
+<!DIRECTIVES("HELPERS: REFLECT")!>
+
+val Boolean.<!ELEMENT(1)!>: Boolean
+    get() {
+        return true
+    }
+
+val Boolean?.<!ELEMENT(2)!>: Boolean
+    get() {
+        return false
+    }
+
+fun Int?.<!ELEMENT(3)!>(x: Boolean): Boolean {
+    return !x
+}
+
+fun box(): String? {
+    if (!false.<!ELEMENT(1)!> || false.<!ELEMENT(2)!> || !0.<!ELEMENT(3)!>(false)) return null
+
+    if (!checkCallableName(Boolean::<!ELEMENT(1)!>, "<!ELEMENT_VALIDATION(1)!>") || !Boolean::<!ELEMENT(1)!>.get(true)) return null
+    if (!checkCallableName(Boolean????::<!ELEMENT(2)!>, "<!ELEMENT_VALIDATION(2)!>") || Boolean????::<!ELEMENT(2)!>.get(false)) return null
+    if (!checkCallableName(Boolean????::<!ELEMENT(2)!>::equals.call(false)::<!ELEMENT(1)!>, "<!ELEMENT_VALIDATION(1)!>")
+        || !Boolean????::<!ELEMENT(2)!>::equals.call(false)::<!ELEMENT(1)!>.get()) return null
+    if (!checkCallableName(Int?::<!ELEMENT(3)!>, "<!ELEMENT_VALIDATION(3)!>") || Int?::<!ELEMENT(3)!>.call(10, true)) return null
+
+    return "OK"
+}