Make DispatchKeyExtractor forget about TensorOptions (#36290)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36290
The BackendSelect dispatch key gives us a way to extract backend-
specific dispatch keys from non-Tensor arguments without teaching
the DispatchKeyExtractor about them. Here we finish switching over
to the BackendSelect approach for factory functions and remove
TensorOptions from the set of types DispatchKeyExtractor needs to
consider.
Test Plan: Imported from OSS
Differential Revision: D20936595
Pulled By: bhosmer
fbshipit-source-id: c2f3cc56776197a792cae2a83aeaca995effaad2
