Enable //test/rustfmt on the Windows CI

[hlopko]

Since #612 we test more stuff on Windows, we don't test everything though. //test/rustfmt is currently disabled in .bazelci/presubmit.yml.

Feel free to comment on this issue if you want to know more or you want to give it a shot. We are happy to talk or help :)

How to fix when you don't have a Windows machine:

1. delete the line with - "-//test/rustfmt/..."
2. upload a draft PR
3. see the CI failure
4. try to fix it

How to fix when you do have a Windows machine:

1. Try to repro the failure localy
2. Fix it
3. upload the PR :)