[iOS] Add UIScene lifecycle events.

[bruvzg]

Fixes #115936

[stuartcarnie]

I can confirm this works.

I would recommend we remove the onChange handler in app.swift, given the lifecycle events are being called again, which also start / stop rendering and audio, and are now superfluous.

@rsanchezsaez may be able to offer additional comments on removing onChange.

[stuartcarnie]

Nice!

[akien-mga]

Thanks!

[Repiteo]

Cherry-picked for 4.6.2.

[jupitersecho]

Hey all,

I needed to stay on Godot 4.5.1, so I backported the iOS UIScene fix from PR #116395 and built patched iOS custom export templates. I wanted to share in case anyone else finds useful.

Repo: https://github.com/JupitersEchoDesigns/godot-4.5.1-ios-uiscene-fix

Release/templates: https://github.com/JupitersEchoDesigns/godot-4.5.1-ios-uiscene-fix/releases/tag/v4.5.1-ios-uiscene-fix-1

This fixed the "UIScene lifecycle will soon be required. Failure to adopt will result in an assert in the future." warning for me on 4.5.1.

Usage is simple. Go into your iOS export, and set the debug and release to point at the patched godot_ios zip. If you wish to revert, just remove the links.

This is not an official Godot release, just a focused 4.5.1 backport for anyone else blocked on the same issue.

Thanks,
Jupiter's Echo