Move callable reference diagnostic tests to non-stdlib

compiler/testData/diagnostics/tests/callableReference/property/extensionPropertyOnNullable.kt

@@ -0,0 +1,10 @@
+// !CHECK_TYPE
+
+val Any?.meaning: Int
+    get() = 42
+
+fun test() {
+    val f = Any?::meaning
+    checkSubtype<Int>(f.get(null))
+    checkSubtype<Int>(f.get(""))
+}