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

^KT-61564

compiler/testData/diagnostics/nativeTests/specialBackendChecks/objCInterop/t33.kt

@@ -0,0 +1,10 @@
+import kotlinx.cinterop.*
+import platform.darwin.*
+import platform.Foundation.*
+
+class Zzz : NSString {
+    @OverrideInit
+    constructor(coder: NSCoder) { }
+
+    override fun initWithCoder(coder: NSCoder): String? = "zzz"
+}