[Upstream] fix (iOS): Only try to make the alert window key if the app recognizes it

[Saadnajmi]

Summary

This is a change we made in our fork (React Native macOS) that we are now upstreaming to reduce the number of diffs between React Native Core and React Native macOS. Also.. one less crash 🥳!

Resolves microsoft#1675

Original PR Notes:

In iOS 14, if we call -[UIWindow makeKeyAndVisible] from a UIWindow that isn't part of the app, the current key window gets made non-key. This can result in RCTKeyWindow(), and thusly, RCTPresentedViewController(), to come back as nil, which means that the alert never shows up.

The fix here is to ensure that we don't try to make the alert window key unless it's actually tracked by the application.

Changelog

[IOS] [FIXED] - Only try to make the alert window key if the app recognizes it

Test Plan

Build should pass. This change has been running in our fork in production for a while so we're fairly confident of it.

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	8,462,911	-19
android	hermes	armeabi-v7a	7,783,489	+208
android	hermes	x86	8,936,172	+272
android	hermes	x86_64	8,794,233	+425
android	jsc	arm64-v8a	9,648,873	-14
android	jsc	armeabi-v7a	8,383,370	+207
android	jsc	x86	9,711,124	+262
android	jsc	x86_64	10,188,137	+422

Base commit: 6f7428e
Branch: main

[Saadnajmi]

This may be a duplicate of #35716

[Saadnajmi]

Closing as there is already a similar fix merged.