This required fixing the override code so that all (not just one) the
parameter types would match. Fixes
```
build/maccatalyst/reference/Xamarin.iOS.cs(11036,50): error CS0115: 'ARSCNView.HitTest(CGPoint, ARHitTestResultType)': no suitable method found to override
build/maccatalyst/reference/Xamarin.iOS.cs(11703,50): error CS0115: 'ARSKView.HitTest(CGPoint, ARHitTestResultType)': no suitable method found to override
```
Follow up to https://github.com/xamarin/xamarin-macios/pull/10658 and
https://github.com/xamarin/xamarin-macios/pull/10678
* Fix system version checks to work properly on Mac Catalyst (which uses the macOS
version as its system version).
* Add the framework-specific defines to the build for monotouch-test.csproj (using
the generated response files), this way we can use them in the tests.
* Sprinkle conditionals in numerous places - I tried using either framework-specific
or XAMCORE_3_0 whenever that made since (instead of using Mac Catalyst as a condition).
* Updated a few tests to use non-deprecated API (because the deprecated API often
doesn't exist in Mac Catalyst).
* Also a few minor API fixes to make any corresponding tests compile.
I obsoleted `GetProjectPoint` in favor of `Project` because of the introduction of `Unproject` (which made me realize the naming was wrong) and based on the API doc https://developer.apple.com/documentation/arkit/arcamera/2923538-projectpoint?language=objc.
The `CGPoint` returned is the projection of a point. An other naming option would have been `GetProjectedPoint` but I think `Project` is closer to the original and clear enough. You project/unproject something onto something else and you get the projection back.
Rolf Bjarne Kvinge
Sebastien Pouliot
Vincent Dondain