CI: Move Windows OS tests to GHA
To hopefully address the annoying timeouts in Windows tests on Azure, moving these tests to GHA.

Azure has a timeout limit of 1 hour: https://docs.microsoft.com/en-us/azure/devops/pipelines/process/phases?view=azure-devops&tabs=yaml#server-jobs

GHA has a timeout limit of 6 hours (among other things): https://docs.github.com/en/actions/learn-github-actions/usage-limits-billing-and-administration#usage-limits

Trying another approach first