Calling Uri.PathAndQuery is not allowed on a relative Uri, which made the
previous Uri -> NSUrl implicit operator always throw if given a relative
NSUrl.
So I fixed that, added several tests, and found another issue (it turns out
that 'url.RelativePath == url.Path' is not a reliable way to detect absolute
urls, because it's true for relative urls as well) and fixed that too.
Fixes https://github.com/xamarin/xamarin-macios/issues/9607.
* Fix many version checks to be based on Xcode version instead of iOS version.
* Added/fixed a few expected values according to platform version to match behavior in older macOS versions.
Rolf Bjarne Kvinge
Whitney Schmidt
Timothy Risi