Handle new iOS location permission event (issue 1390)

[msjogren]

Description of Change

Adapts code to new CLLocationManager APIs in iOS 14 (tvOS 14, watchOS 7) while keeping existing logic for older versions.

Bugs Fixed

• Fixes [Bug] in iOS 14 await Permissions.RequestAsync<Permissions.LocationXXX>() does not return after the pop-up is closed #1390

API Changes

None

Behavioral Changes

None

PR Checklist

• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Updated documentation (see walkthrough)

[ghost]

All CLA requirements met.

[mattleibow]

@msjogren thanks for this PR. It pretty much does everything right.

I hope you don't mind that I pushed to your branch. I was trying a few things on what you did and I replaced the events with a delegate class. I as trying to find a way to not use the new members so we can support VS 2017 for a tiny bit longer. I'm going to probably push out a PR NuGet to the preview feed for anyone with VS2017 to test.

[msjogren]

@mattleibow Not at all, I like your version even better. I didn't realise it would cause issues with VS2017.

[MitchBomcanhao]

@msjogren does this change force us to be on xcode 12? we're still on xcode 11.5 due to some package namespace conflicts in AppCenter, and when updating to essentials 1.6.0 the build will fail

MTOUCH : error MT2101: Can't resolve the reference 'CoreLocation.CLAuthorizationStatus CoreLocation.CLLocationManager::get_AuthorizationStatus()', referenced from the method 'System.Void Xamarin.Essentials.Permissions/LocationWhenInUse/ManagerDelegate::DidChangeAuthorization(CoreLocation.CLLocationManager)' in 'Xamarin.iOS

[msjogren]

@MitchBomcanhao It requires Xamarin.iOS 14. I don't have a machine around to try but according to this you may still be able to use an older version of Xcode.