[dtensor] PART 6: move DTensor op tests to core distributed (#88551)
This PR moves DTensor op tests to core distributed, including
prop_rule, pointwise op, matrix op tests, etc.
part of https://github.com/pytorch/pytorch/issues/88838
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88551
Approved by: https://github.com/aazzolini
