View-only layout ops mover

[CC-Yeh]

Proposed changes

View-only layout ops (e.g. expand_dims, squeeze) can sit between elementwise ops and reduce compile’s fusion opportunities.

This PR adds a small “layout mover” step in compile_simplify that (conservatively) rewrites view(op(x)) -> op(view(x)), and runs it to a bounded fixpoint so the view can move up multiple elementwise layers.

This is an early draft to get feedback on whether MLX wants this optimization before I refine/extend it (e.g. consider reshape, flatten ...).

Before:

After:

Checklist

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

[CC-Yeh]

@awni @angeloskath

What do you think about adding this to compile?
It's a bit similar to XLA ReshapeMover.