For policy-specific tests, use the version before the policy was
introduced. Otherwise, use 3.5 where possible.
Also, remove `cmake_minimum_required()` and `project()` calls from
individual cases where they are handled by `CMakeLists.txt`.
When support for `DOTNET_SDK` was added, only a minimal set of options
were built in. Based on user feedback, support for reference to dlls
(not just projects) is needed. That support is added here.
Fixes: #23166
Changes in cmVisualStudio10TargetGenerator::Generate to write .Net
SDK-style project for VS generators VS 19 and above. Also adds
documentation and tests.
Issue: #20227
Brad King