Revert "Put Python Dispatcher cache in dict, clear it on new registrations. (#88329)"
This reverts commit 86c7cd287caeb23c227d97d283e58bc123294746.
Reverted https://github.com/pytorch/pytorch/pull/88329 on behalf of https://github.com/clee2000 due to test_decomp takes an extra 2 hours in some jobs, windows takes so long it times out