Execute Windows installer integration tests on several Windows versions (#7641)
Execute Windows installer integration tests on several Windows versions (#7641)

This PRs extends the installer tests on Azure Pipeline, in order to run the integration tests on a certbot instance installed with the Windows installer for several Windows versions, corresponding to the scope of supported versions on Certbot:
* Windows Server 2012 R2
* Windows Server 2016
* Windows Server 2019

One can see the result on: https://dev.azure.com/adferrand/certbot/_build/results?buildId=311

* Try specific installer-build step

* Install Python manually

* Add tests on windows 2019

lmcro/letsencrypt,letsencrypt/letsencrypt,stweil/letsencrypt,letsencrypt/letsencrypt,stweil/letsencrypt,lmcro/letsencrypt