windows-ci: run Windows CI automatically alongside the others
This will enable us to make Windows Python 3 a first-class citizen for the next
6.0 cycle. We will probably get some flaky tests and we're missing others that
are skipped, but we'll turn them on it future patches.
Differential Revision: https://phab.mercurial-scm.org/D11256
#require docutils gettext
$ $TESTDIR/check-gendoc sv
checking for parse errors