Merge index_{add,fill,copy,select} sampling (#68184)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68184
This was in the TODO list as the three operations are very similar.
Did this as one of them was failing in the noncontig tests and I wanted
to make sure that all of them were tested properly, as they all appear
in the derivative formulas of each other.
After this PR, these operations do pass the noncontiguous tests.
cc mruberry
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D32684854
Pulled By: mruberry
fbshipit-source-id: 5db58be8d1e1fce434eab9cdf410cbf1024bbdf9
