port div to structured (#53680)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53680
Porting `div` to structured.
One weird thing to call out with div: It has an overload, `div.Tensor_mode`, which uses different TensorIterator settings depending on this input (the "mode" argument that you pass to it). So I ended up switching on the mode inside of the meta function to determine which TensorIterator builder to use.
Test Plan: Imported from OSS
Reviewed By: ezyang
Differential Revision: D27029819
Pulled By: bdhirsh
fbshipit-source-id: 3f216f6c197a2321087b4c23202bc2fc561491ba
