Windows CI support: Add unit tests only to the PR gate - start with buildTools only.

[minalsha]

Is your feature request related to a problem? Please describe.
coming from #1448 wherein goal is to add unit tests only to the PR gate, start with buildTools only for Windows.

[minalsha]

@mch2 do we need do any work for this issue?

[mch2]

I think we should close this issue. Few if any these test suites are able to run on GH as a gate, and provide little value. We should instead move the entire check on PR from Jenkins.