C++ API parity: AdaptiveAvgPool1d
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/26808
Test Plan: Imported from OSS
Differential Revision: D17627827
Pulled By: pbelevich
fbshipit-source-id: 13ad1d0414e7b62f4fc2f6573332bb2c07b16b53
