Fix preview orientation on iOS

[janusw]

This fixes #19 by using UIInterfaceOrientation instead of UIDeviceOrientation. Tested on iOS 16.7.6 and 17.4 (with an iPhone and iPad).

It also extends the test app to allow all four interface orientations on iPhones (PortraitUpsideDown was missing).

[janusw]

Note: The GHA build shows the warning

This call site is reachable on: 'iOS' 11.0 and later, 'maccatalyst' 13.0 and later.
'UIApplication.Windows' is obsoleted on:
'ios' 15.0 and later (Use 'UIWindowScene.Windows' in the desired window scene object instead.),
'maccatalyst' 15.0 and later (Use 'UIWindowScene.Windows' in the desired window scene object instead.).
(https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1422)

However, the call still seems to work on iOS 16 & 17.

[janusw]

Moreover, on the same line, there also is this warning:

This call site is reachable on: 'iOS' 11.0 and later, 'maccatalyst' 13.0 and later.
'UIWindow.WindowScene' is only supported on: 'ios' 13.0 and later.
(https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1416)

I think the warning is incorrect, because the line is guarded by OperatingSystem.IsIOSVersionAtLeast(13). AFAICS this is due to the following diagnostic bug: dotnet/roslyn-analyzers#7239
See also: dotnet/maui#21106

[janusw]

Note: The GHA build shows the warning

This call site is reachable on: 'iOS' 11.0 and later, 'maccatalyst' 13.0 and later.
'UIApplication.Windows' is obsoleted on:
'ios' 15.0 and later (Use 'UIWindowScene.Windows' in the desired window scene object instead.),
'maccatalyst' 15.0 and later (Use 'UIWindowScene.Windows' in the desired window scene object instead.).
(https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1422)

However, the call still seems to work on iOS 16 & 17.

This deprecation warning is fixed in commit 062e8dc via the method used in https://www.delasign.com/blog/swift-device-orientation/. This should make the code more future-proof.

As before, I tested this on iOS 16 & 17 (with the front and back camera).