Add SparseLengthsSum4BitRowwiseSparse in c2_pt_converter (#48240)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48240
Adds the support for converting the SparseLengthsSum4BitRowwiseSparse operator from caffe2 to pytorch as a part of c2_pt_converter
Test Plan:
Added a unit tested
buck test //caffe2/torch/fb/model_transform/c2_convert:c2_pt_converter_test
Tests Passed :
https://our.intern.facebook.com/intern/testinfra/testrun/2251799856412296
Reviewed By: houseroad
Differential Revision: D25067833
fbshipit-source-id: 45cbc331ca35bee27e083714e65a1e87a2a2d2e0
