* [tests] Use Assert.Throws instead of the ExpectedException attribute.
The ExpectedExceptionAttribute doesn't exist in newer versions of NUnit[Lite] anymore.
* [monotouch-test] Rework some CaptiveNetwork tests.
They need permissions, and entitlements, and something else I couldn't figure
out, so just assert they're returning null instead.
* 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
Timothy Risi