[nnc] Update block and thread extents in cuda_codegen to use int64_t (#71428)
Summary:
The block and thread extent calculations in `cuda_codegen` should be using `int64_t` instead of `int`. The updated test, `test_dynamic_shapes`, fails without this change.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71428
Reviewed By: samdow
Differential Revision: D33640374
Pulled By: navahgar
fbshipit-source-id: 64c340ad2a9a1fa1fe066cf1c5dfc3b546b7be6d
(cherry picked from commit 6ea546ce116fc05d9d7e225bc29f7fe86be439de)
