Use the XAJavaInterop1 codegen by default

[Redth]

See: https://docs.microsoft.com/en-us/xamarin/android/deploy-test/building-apps/build-process#binding-project-build-properties

Basically, smaller, faster bindings - this does require 6.1 or later, so there's a condition for that.

This also bumps TargetFrameworkVersion to something a bit more sane (really I'd like to see this go to 9.0)

[clairernovotny]

Thanks!

For the min version, keep in mind that only applies if someone specifies MonoAndroid. If they put in a version, like MonoAndroid80 or MonoAndroid9, that'll always win.

[Redth]

Yup, true, just like pushing our users to newer versions of android to target, especially now that Google is enforcing this more strictly in the play store.