Propagate dynamic int on `__setitem__`. (#105923)
Fix: #105533
This PR propagates dynamic ints used as indices for `__setitem__`. In summary, we:
- Replace the integer type for `TensorIndex` (both the enum and the corresponding
functions)
- Accordingly modify _python_variable_indexing.cpp_
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105923
Approved by: https://github.com/ezyang
