[dtensor] PART 3: move most DTensor ops to core distributed (#88177)
This PR moves most DTensor ops to torch.distributed._tensor. We will
add all tests in the following PRs.
part of https://github.com/pytorch/pytorch/issues/88838
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88177
Approved by: https://github.com/fduwjj
