Add C++ torch::nn::CosineEmbeddingLoss (#27345)
Summary:
Adds `torch::nn::CosineEmbeddingLoss` module and functional support for the C++ API.
Issue: https://github.com/pytorch/pytorch/issues/25883
Reviewer: yf225
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27345
Differential Revision: D17801402
Pulled By: yf225
fbshipit-source-id: 0eabe80d7d36397e6667b331c3fa2f56d7a15962
