[1/n]support double for Caffe2 ScatterWeightedSum (#60402)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60402
Add float64 data type support for ScatterWeightedSum for cases that 10^7 precision is not sufficient.
Test Plan: buck test caffe2/caffe2/python/operator_test:sparse_ops_test -- testScatterWeightedSum
Reviewed By: jianyuh
Differential Revision: D29190324
fbshipit-source-id: 871a60744694e901a2c7685a67350860745d6729
