[3/N] Refine beginner tutorial by accelerator api

[guangyey]

For #3113

Motivation

• -> [3/N] Refine beginner tutorial by accelerator api #3170
• [2/N] Refine beginner tutorial by accelerator api #3168
• [1/N] Refine beginner tutorial by accelerator api #3167

As titled, we aim to use accelerator API to refine the beginner model tutorial to make it device-agnostic.

Checklist

• The issue that is being fixed is referred in the description (see above "Fixes #ISSUE_NUMBER")
• Only one issue is addressed in this pull request
• Labels from the issue that this PR is fixing are added to this pull request
• No unnecessary issues are included into this pull request.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/tutorials/3170

• 📄 Preview Python docs built from this PR

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[albanD]

Sounds good to me.
Will let @svekars take a final look.