[MPS] Fix printTensor() for MPS (#86534)
MPS does not support double type, so tensor need to be cast to CPU first
before it can be cast to double.
Also, do a little bit of BE, by initializing values and marking unused range variables with C10_UNUSED
Fixes https://github.com/pytorch/pytorch/issues/86410
Pull Request resolved: https://github.com/pytorch/pytorch/pull/86534
Approved by: https://github.com/weiwangmeta
