Setup Windows CI environment

[iandunn]

Would bugs like #47980 be more likely to be caught before release if we had a Windows environment setup in Travis, and/or ​test results from a Windows host?

If so, there may still be some things like #40856 that would need to be resolved first, though.

[ocean90]

Related: #44276

[johnbillion]

I was under the impression that Bytemark were providing Windows boxes for the hosting testing. Maybe it never happened.

[ayeshrajans]

It does look like Travis has support for Windows now, so it wouldn't be impossible to add Windows builds to Travis. I can also see Appveyor file already in for npm scripts. Perhaps we can run the test suite there too?

[desrosj]

I have been putting some thought into this while converting our test environment from TravisCI to GitHub Actions in #50401. Here is where I am at:

• Appveyor is going to be removed through #51968.
• It's super easy to test on Windows using GitHub actions.
• Windows testing could probably be done on a scheduled cron instead of every commit. I can't find actual usage numbers, but my guess is that usage is significantly lower.
• The bridge network driver used in the Docker configuration is incompatible with Windows. (​https://docs.docker.com/network/). I did some rough testing, and it seems not specifically defining bridge as the driver fixes the issue and does not break testing on other environments, as Docker falls back to the default network driver for the OS being used. However, I am not sure why bridge was chosen originally, or if there are any adverse affects I did not spot.