[CI] Jenkins on Windows builds

[BarclayII]

Description

Added Windows build & unit/example tests on PyTorch/CPU. The backend is built with MSBuild and MinGW is no longer required.

Checklist

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [$CATEGORY] (such as [Model], [Doc], [Feature]])
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• To the my best knowledge, examples are either not affected by this change,
  or have been fixed to be compatible with this change

[VoVAllen]

Is jenkins workspace on windows reused by different commit? Since it's not docker, do we need to clean the directory or other environment we've used at the end of the process?
Also it's better to indicate which pytorch version is used in windows build.

[BarclayII]

Jenkins will have a dedicated workspace for each branch/PR so I think reusing the workspace should be fine. As long as we are cleaning up the build directory (which we do) then we should be safe.

[VoVAllen]

Thanks! Looks good to me.

[jermainewang]

LGTM