Add aten::avgpool2d NNAPI converter (#58538)
Summary:
Add support for aten::avgpool2d op in the NNAPI model converter with var
size support
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58538
Test Plan: pytest test/test_nnapi.py::TestNNAPI::test_avgpool2d
Reviewed By: anshuljain1
Differential Revision: D28531944
fbshipit-source-id: 43ff8c9389365698c282f204042b49c7ec84d824
