perf: avoid extra Vec allocation in split_structs

[Galoretka]

Summary

Replace output_split.vars.to_vec() in the StructDestructure handling with output_split.vars.iter().cloned() so we no longer allocate a temporary Vec just to iterate over it.

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Type of change

• Performance improvement

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Why is this change needed?

Avoid per-statement heap allocation in a hot optimization pass.

[reviewable-StarkWare]

This change is 

[orizi]

@orizi reviewed 1 file and made 1 comment.
Reviewable status: all files reviewed (commit messages unreviewed), 1 unresolved discussion (waiting on @Galoretka).

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crates/cairo-lang-lowering/src/optimizations/split_structs.rs line 177 at r1 (raw file):

                                ctx.var_remapper.renamed_vars.insert(*output, new_var).is_none()
                            )
                        }

Suggestion:

                        for (output, new_var) in zip_eq(&stmt.outputs, &output_split.vars) {
                            assert!(
                                ctx.var_remapper.renamed_vars.insert(*output, new_var.clone()).is_none()
                            )
                        }

[orizi]

@orizi reviewed 1 file and all commit messages, made 1 comment, and resolved 1 discussion.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Galoretka).