Add smollm3 to ET

[jackzhxng]

Summary

Was from a while ago, perf ended up being similar to Optimum ET so decided not to go further. But putting this out here anyways just in case

Test plan

Verified output with C++ runner

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/13011

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✅ No Failures

As of commit 8985529 with merge base 953fa0e ():
💚 Looks good so far! There are no failures yet. 💚

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