[NNAPI] Add support for unsqueeze, cat, and mean (#48811)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/48811
Test Plan: Unit tests.
Reviewed By: axitkhurana
Differential Revision: D25317936
Pulled By: dreiss
fbshipit-source-id: 9b3a0a75b8157ae35ac13d52293a67800bad0ded
