Fix status to only point to a CI job that runs on main (after merge)

[richardpringle]

Right now, our "CI" status points to the CI job that runs on PRs instead of that same job just running on main. We could add on to the job that builds the main cache also to run tests to prove that tests are passing on the main branch and use that status to that job instead. In that case, we would also want to rename that job.