Revert "test in parallel at file granularity (#84961)"
This reverts commit 8107666c6a1c25e96762a31296cace9ed343aaf6.
Reverted https://github.com/pytorch/pytorch/pull/84961 on behalf of https://github.com/clee2000 due to makes test_forward_ad_nn_functional_max_unpool2d_cuda_float32 flakily unexpectedly pass
