Always run prioritized tests first, even if they're expected to run serially (#100748)
Today, we prioritize running test files that were edited in the user's PR, with the idea being to run them before we run any other test.
Except, if the modified test is supposed to run serially, then we still end up running it after all the parallelized tests have finished running.
This PR fixes that to _always_ run the prioritized tests before the regular tests, regardless of if the test is supposed to run serially or in parallel
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100748
Approved by: https://github.com/huydhn
