perf: avoid redundant String clones in doc parser

[Bashmunta]

Summary

This change removes unnecessary String allocations when parsing documentation links. The link resolver now accepts &str instead of owning a String, and the CommentLinkToken Display implementation no longer clones its path field.

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Type of change

Please check one:

• Performance improvement

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Why is this change needed?

As a result, we reuse a single String instance per link and pass references into the resolver, keeping the behavior unchanged while reducing allocation overhead in the documentation parser.

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[reviewable-StarkWare]

This change is 

[orizi]

@orizi made 1 comment.
Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @Bashmunta).

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crates/cairo-lang-doc/src/parser.rs line 219 at r1 (raw file):

                                _ => {
                                    let path = dest_url.clone().into_string();
                                    let resolved_item = self.resolve_linked_item(item_id, &path);

this still alocates the string in the SmolStrId::from - so not really any better.