Specialize LengthsRangeFill and SparseLengthsWeightedSum in bound shape inference (#16869)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16869
TSIA.
Reviewed By: ipiszy, rdzhabarov
Differential Revision: D13994946
fbshipit-source-id: 7e507abc5a3c2834c92910e521387085c56e8b2e
