[caffe2] move fused SparseAdagrad to open source (#35164)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35164
As title
Test Plan: CI
Reviewed By: jianyuh
Differential Revision: D20581853
fbshipit-source-id: 393ddd9487cd965c465eaa49e1509863618a6048
