test in parallel at file granularity (#84961)
run tests in parallel at the test file granularity
runs 3 files in parallel using multiprocessing pool, output goes to a file, which is then printed when the test finishes. Some tests cannot be run in parallel (usually due to lacking memory), so we run those after. Sharding is changed to attempt to mask large files with other large files/run them on the same shard.
test_ops* gets a custom handler to run it because it is simply too big (2hrs on windows) and linalg_cholesky fails (I would really like a solution to this if possible, but until then we use the custom handler).
reduces cuda tests by a lot, reduces total windows test time by ~1hr
Ref. https://github.com/pytorch/pytorch/issues/82894
Pull Request resolved: https://github.com/pytorch/pytorch/pull/84961
Approved by: https://github.com/huydhn
