[iOS GPU][BE][1/n] - Remove unused headers + improve error message (#53428)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53428
Start to do some code clean up work.
ghstack-source-id: 123038070
Test Plan:
- CircleCI
- Sandcastle CI
- AIBench
Reviewed By: SS-JIA, AshkanAliabadi
Differential Revision: D26681115
fbshipit-source-id: b1b7cfc6543b73928f517cd52e94a2664ee0bd21
