improve CI runners for slow tests

[atravitz]

#1131 (comment)

[jameseastwood]

This would be nice-to-have, @atravitz and @mikemhenry please discuss whether you can do it this iteration or not

[mikemhenry]

This includes getting the CPU runners working as well

[jameseastwood]

We should make sure we're not running codecov if we don't need to.

[atravitz]

tests are efficient enough for now, and I think our execution of codecov is fine! closing.