Removes AppVeyor and all Travis jobs but the iOS one, which hasn't been ported to GitHub Actions yet (should be done soon). Backports new style scripts from `master` branch too to do the same checks.
Removes AppVeyor and all Travis jobs but the iOS one, which hasn't been ported to GitHub Actions yet (should be done soon). Backports new style scripts from `master` branch too to do the same checks.