[K/N] Move special backend checks test sources to diagnostic tests folder

^KT-61564

compiler/testData/diagnostics/nativeTests/specialBackendChecks/objCInterop/t61.kt

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+// KT-50109
+class Foo {
+    companion object : platform.darwin.NSObjectMeta()
+}