Mark them as NI so that in the fugure they might be turned back
on if they can be made to work. Keep the tests around as reference.
Also, remove reports that are no longer tested in CI. This is because
they are no longer tested by a previous patch that relies on the
change vvp_reg.pl behavior around failed tests.
Remove now obsolete update_msys2_report.pl, and simplify the test.sh
script, since diff commands and Windows specific trickery are no
longer needed.
If there are any failures, return a non-zero exit status so that
invoking scripts can detect that failures happen. This eliminates
the need to use regression report reference outputs, and should
make it easier to merge PRs that add or impact tests.
By adding ivtest to the iverilog source tree, it is easier to keep
the regression test synchronized with the source that is being tested.
This should be especially helpful for PRs that add a new feature, and
have a matching ivtest PR with the regression test for that feature.