Essentials Location Permissions Set result after cleanup of iOS LocationManager

[jfversluis]

Description of Change

Port of this change in Xamarin.Essentials: xamarin/Essentials#1815

On IOS if you like to request LocationAlways you have to request locationWhenInUse first. This means in an average implementation one would have 2 consecutive calls
await Permissions.RequestAsync<Permissions.LocationWhenInUse>();
await Permissions.RequestAsync<Permissions.LocationAlways>();
Both use the static LocationManager instance.
Since RequestAsync<Permissions.LocationWhenInUse>() sets the result of the task completition source before cleaning up its locationManager there is a race condition where RequestAsync<Permission.LocationAlways>() already runs and thus this cleanup disposes the locationManager used by the second call. This will not always be the case but in my test around 50% of the time. Workaround wait 3-10 seconds in between the calls

Issues Fixed

Original Xamarin.Essentials bug: xamarin/Essentials#1489