Improve error message when Visual C++ or standard libraries cannot be found on Windows

The Visual C++ and Windows DSK resolution includes a bunch of logic and validation that can go wrong. When it does, the error message presented to the user basically says "Visual Studio not found" but it doesn't say _why_, making issues difficult to diagnose.

The error message should include which candidate installs were considered, if any, and why each one was rejected. This can give some clues to a user to help them figure out whether the problem lies with their machine configuration or with Gradle or something else.

A concrete example: A fresh install of visual studio 2015 community edition does not include visual c++. The user has to first attempt to create a new c++ project before it is installed (no doubt there are other ways to trigger this). Currently, if you forget to do this step, Gradle says "Visual studio not installed", even though it in fact is. It would be much more useful if instead Gradle said "visual studio install x does not seem to include a visual c++ install, looked in y directory".

Locate the Visual C++ and Windows SDK resolution and validation logic, then inspect where the current "Visual studio not installed" message is produced. The work is complete when the error reports considered candidate installations and explains why each was rejected, including missing Visual C++ components or searched directories.

Written by the indexing model from the issue text.