Re-inplace slice_copy with slice

[metascroy]

🚀 The feature, motivation and pitch

Before to_executorch, there are view_copy nodes in the graph. During to_executorch, we replace view_copy nodes with view nodes before memory planning: https://github.com/pytorch/executorch/blob/main/exir/program/_program.py#L757-L761

These get emitted to view ops here: https://github.com/pytorch/executorch/blob/main/exir/emit/_emitter.py#L944-L978

The view op is implemented here: https://github.com/pytorch/executorch/blob/main/kernels/prim_ops/et_view.cpp

We want to do the same for contiguous slices. If a graph has a contiguous slice, we want to replace it with a lightweight slice kernel, rather than a slice_copy kernel.

If interested in this task, please reach out to @metascroy. Happy to guide you through it :)

cc @JacobSzwejbka

Alternatives

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Additional context

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RFC (Optional)

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[JacobSzwejbka]

Ideally this pass works for other dim orders then the default but that can be a follow up