Try running provider tests in parallel under CI.

[jmalloc]

They currently take nearly 2 minutes to run what usually takes a few seconds locally.

They already run "in parallel" because the Go test runner does, but I'm suggesting splitting them into separate jobs (not sure of terminology) in the workflow such that the necessary docker container (mysql, postgres, etc) launch in parallel, followed by the tests for that package running alone.

The hard part about this will be working out how to combine the coverage reports afterwards. I suspect it should be possible using "artifacts" or equivalent in GHA, to keep the .cov files from each job. We may not even have to merge the .cov files in order to send them to codecov.io. If we do, we might be able to use gocovmerge like we did in the old makefiles before Go did this itself.