Add prompt completion e2e code

[qqlabs]

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[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/torchtune/1907

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[ebsmothers]

Hi @qqlabs thanks for creating the PR, this is an interesting use case. One thing that we are trying to do more of is provide examples of how people can use torchtune in their own projects and I feel like this could be a great case for that. I wonder if you'd be interested in providing this as a standalone example (either as a fork of torchtune, or a separate repo taking a dependency on torchtune). If so, we'd be happy to highlight it as a community recipe!