fix(devtools-ios): Ensure UI modifications run on main thread

Modifications to the UI can only be made from the main thread.
Since {N} 5.3.0 all debugger protocol messages are processed
by the worker thread that receives them in iOS.

refs #7219, https://github.com/NativeScript/ios-runtime/pull/1101

tns-core-modules/utils/utils.ios.ts

@@ -159,6 +159,14 @@ export function openUrl(location: string): boolean {
     return false;
 }
 
+export function executeOnMainThread(func: () => void) {
+    NSOperationQueue.mainQueue.addOperationWithBlock(func);
+}
+
+export function isMainThread(): Boolean {
+    return NSThread.isMainThread;
+}
+
 class UIDocumentInteractionControllerDelegateImpl extends NSObject implements UIDocumentInteractionControllerDelegate {
     public static ObjCProtocols = [UIDocumentInteractionControllerDelegate];