Introduce periodic.yml (#4348) #2007

Job	Run time
build-llm-demo (bpe) / linux-job	30m 35s
build-llm-demo (tiktoken) / linux-job	37m 52s
upload-artifacts	1m 35s
test-llama-app (bpe) / mobile-job (android)	4m 1s
	1h 14m 3s

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