GitHub has removed the runner image.
A breakage with CLMUL CRC code occurred with VS 2019 but not 2022,
see b5a5d9e3f702. MS supports VS 2019 for a few more years, so it's
unfortunate that it can no longer be tested on GitHub.
Sometimes the VM workflows (like FreeBSD VM on Ubuntu) get stuck
and the default timeout is six hours. While at it, set a sensible
timeout for all workflows.
Using eight runners seems wasteful. Using only two runners isn't
much slower due to the runner startup overhead.
Also add a comment about the test that fails without b5a5d9e3f702.
