🐛 Describe the bug

First time contributors are welcome! 🙂
Add support for aten::sgn.out for MPS backend. Generic support for adding operations to MPS backend is captured here: https://github.com/pytorch/pytorch/wiki/MPS-Backend#adding-op-for-mps-backend

Versions

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cc @kulinseth @albanD @malfet @razarmehr @abhudev