Add LLaMA perf benchmark workflow for Apple iOS #16

Job	Run time
set-parameters	15s
export-models (stories110M, xnnpack) / macos-job	12m 29s
build-llm-demo (bpe) / macos-job	13m 8s
upload-models	20s
upload-ios-apps	18s
benchmark-on-device (stories110M, xnnpack, arn:aws:devicefarm:us-west-2:308535385114:devicepool:0... / mobile-job (ios)	25m 0s
	51m 30s

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