Enforce type promotion in `torch.cat` (#35030)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/35014
CUDA `cat` implementation doesn't use `TensorIterator` so there is the need of manually doing some checks in the code.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35030
Differential Revision: D21155853
Pulled By: nairbv
fbshipit-source-id: 9e78bb7591f806734e12555831157061c925ff40
