* Change the generator to not write the version in SupportedOSPlatform
attributes unless it's greater than min OS version.
* Fix a few redundant Mac Catalyst availability versions.
* Uncomment the test to verify that availability attributes don't include
useless version information.
Fixes https://github.com/xamarin/xamarin-macios/issues/11029.
Port the availability attribute test from introspection to cecil-tests. It's much
easier and faster to test attributes using Cecil using a desktop executable than
having to execute a test app on each target platform.
This also means that we can make the ApiAvailabilityTest in introspection
legacy-only.
Ref: https://github.com/xamarin/xamarin-macios/issues/10834
Rolf Bjarne Kvinge