[TensorExpr] More python binding cleanups (#60058)
Summary:
A few more quality of life improvements for NNC's python bindings:
- Use standard `torch.dtype`s (rather than `te.Dtype`)
- Make names optional (they don't seem to matter)
- Make shapes optional
- A few implicit conversions to make code cleaner
Followup to https://github.com/pytorch/pytorch/issues/59920
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60058
Reviewed By: bertmaher
Differential Revision: D29151953
Pulled By: jansel
fbshipit-source-id: c8286e329eb4ee3921ca0786e17248cf6a898bd8
