Bump Ubuntu-based workflows to ubuntu-22.04 from ubuntu-latest (which is ubuntu-20.04). The newer ubuntu-22.04 image comes with the version of shellcheck (0.8.0) that we want.. which will prevent the GH Actions workflow from failing. Bumped the other Ubuntu workflows as well to maintain consistency (suggested by @abosh)
While at it, bumping macOS version from macos-latest (which is macos-11) to macos-12.