Add a script to run iOS test app on AWS Device Farm (#110202)
This adds a script to test PyTorch on actual iOS devices on AWS Device Farm. The test could take quite a long time pending for the devices to become available, so the steps are done manually and documented in `ios/TestApp/README.md`.
### Testing
1. TestApp itself runs fine on my local iPhone 13 and on [device farm](https://us-west-2.console.aws.amazon.com/devicefarm/home#/mobile/projects/b531574a-fb82-40ae-b687-8f0b81341ae0/runs/d2653ca8-8ee2-44dd-b15e-0402f9ab0aca). I can see the benchmark results output at the console log.
```
BUILD_LITE_INTERPRETER=1 USE_PYTORCH_METAL=1 USE_COREML_DELEGATE=1 IOS_PLATFORM=OS IOS_ARCH=arm64 ./scripts/build_ios.sh
pushd ios/TestApp/benchmark
ruby setup.rb --lite 1 -t 9HKVT38N77 --benchmark
popd
ruby scripts/xcode_build.rb -i build_ios/install -x ios/TestApp/TestApp.xcodeproj -p "OS"
```
2. Trying to run TestAppTests https://github.com/pytorch/pytorch/blob/main/ios/TestApp/TestAppTests/TestLiteInterpreter.mm on my local iPhone ends up with this error `Logic Testing Unavailable. Logic Testing on iOS devices is not supported. You can run logic tests on the Simulator`. I update the xcode project to reuse TestApp as the host application.
```
ruby setup.rb --lite 1 -t 9HKVT38N77
```
3.. Trying [another round of testing on device farm](https://us-west-2.console.aws.amazon.com/devicefarm/home#/mobile/projects/b531574a-fb82-40ae-b687-8f0b81341ae0/runs/18dbd69d-8608-46d8-a868-bd05b69375db)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/110202
Approved by: https://github.com/kit1980
