Fix keyWindow.rootViewController nullability on iOS

[Ponyets]

• This is a small change
• This change has been discussed in issue #<?> and the solution has been agreed upon with maintainers.

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Description:

Issue: #1230

Some iOS developer use [UIApplicaiton sharedApplication].keyWindow.rootViewController as a convenient way to get a VC instance. Surely, this isn't suggested, but it's widely used anyway.
When the app is driven by Detox, this call would return null. It's because DTXTouchVisualizerWindow has a very high windowLevel and doesn't has any ViewController.

This PR fixes this issue by avoid making DTXTouchVisualizerWindow the keyWindow.

[LeoNatan]

I don't think this is the right solution. It can be often incorrect when several UIWindow instances exist (more complex apps). The PR assumes that there is only one user window, but that could be a very wrong assumption.

I don't think it's the right move to break Detox for complex apps in favor of apps that cannot be bothered to use iOS APIs correctly.

If I could suggest something else, but I don't have time to check. If you could test with that instead, I will be happy to include it. UIWindow has a private method called - (BOOL)_canBecomeKeyWindow;

So if we define this method for the touch indicator window, like so:

- (BOOL)_canBecomeKeyWindow
{
	return NO;
}

It could solve the problem people are seeing?

[LeoNatan]

Thanks for checking! I will accept it.

[LeoNatan]

Thanks for checking! I will accept it.