Enable Python code coverage on Windows

[malfet]

Add new config or modify existing one to run and report python code coverage on Windows

cc @ezyang @seemethere @malfet @walterddr @peterjc123 @maxluk @nbcsm @guyang3532 @gunandrose4u @smartcat2010 @mszhanyi

[guyang3532]

What should I do to set up the codecov job for windows? @malfet Any suggestion?

[malfet]

@guyang3532 It should be pretty simple:

• Add coverage and codecov packages to
  

  pytorch/.jenkins/pytorch/win-test-helpers/setup_pytorch_env.bat

  Line 42 in 8acce55

  pip install "ninja==1.10.0.post1" future "hypothesis==4.53.2" "librosa>=0.6.2" psutil pillow unittest-xml-reporting

• Add export PYTORCH_COLLECT_COVERAGE=1 to https://github.com/pytorch/pytorch/blob/master/.jenkins/pytorch/win-test.sh
• Run python3 -mcodecov after tests have finished. For Linux I did it in "Report results" stage:
  

  pytorch/.circleci/verbatim-sources/job-specs/pytorch-job-specs.yml

  Lines 212 to 216 in 8acce55

  	echo "Retrieving coverage report"
  	docker cp $id:/var/lib/jenkins/workspace/test/.coverage ./test
  	docker cp $id:/var/lib/jenkins/workspace/test/coverage.xml ./test
  	python3 -mpip install codecov
  	python3 -mcodecov

  
  But for Windows it can be done differently (especially considering that reports do not need to be extracted from within the docker image)