[PyTorch] Add IValue::toDimVector & mostly replace toIntVector with it (#71247)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71247
Most uses of toIntVector() were for a Tensor shape. We have DimVector to avoid heap allocations in those cases, so let's use it.
ghstack-source-id: 146933314
Test Plan: CI -- if we think DimVector is good in general then I think we have to think this change is good?
Reviewed By: mikeiovine
Differential Revision: D33556198
fbshipit-source-id: cf2ad92c2d0b99ab1df4da0f6843e6ccb9a6320b
