PerformFetch iOS lifecycle delegate lacking an extension method

[davidbritch]

Description

This PR adds a PerformFetch override to MauiUIApplicationDelegate, and adds it as an iOS lifecycle delegate.

What it doesn't do is add it as extension method to iOSLifecycleBuilderExtensions. AFAIK, it's the only iOS lifecycle delegate that doesn't have a corresponding extension method.

This means you have to use the AddEvent method to consume PerformFetch, which is a different pattern.

At the same time, PerformFetch is actually deprecated on iOS (see https://developer.apple.com/documentation/uikit/uiapplicationdelegate/1623125-application), so maybe no time should be wasted here other than obsoleting it.

Steps to Reproduce

No response

Link to public reproduction project repository

No response

Version with bug

8.0.0-rc.1.9171

Is this a regression from previous behavior?

No, this is something new

Last version that worked well

Unknown/Other

Affected platforms

iOS

Affected platform versions

No response

Did you find any workaround?

Use AddEvent to consume the PerformFetch iOS lifecycle delegate.

Relevant log output

No response

[mattleibow]

Related, I always see this in the logs:

2023-10-13 08:41:38.800 TapGestureIssue[69624:2609915] You've implemented -[ application:performFetchWithCompletionHandler:], but you still need to add "fetch" to the list of your supported UIBackgroundModes in your Info.plist.

We probably need to override RespondsToSelector and do a check to return false - but that may be iffy.

[jfversluis]

Looks like we need to deprecate all the above and make this available: https://developer.apple.com/documentation/BackgroundTasks/BGAppRefreshTask