Speed up github actions test suite

[jstockwin]

Perhaps we should try and parallelize GH actions tests into suites. Although the jobs don't get canceled, the tests take over an hour (edit: 20 mins if passing, but can be over an hour if failing) in series. That said, the build time of the container is 20 mins so I'm not sure how much we can help this. If we can cache the containers somehow that would be perfect.