Rust: Implement toString for struct fields and visibility

[paldepind]

Implements toString for StructField and Visibility.

[Copilot]

Pull request overview

This PR implements custom toString methods for StructField and Visibility AST nodes in the Rust CodeQL library, improving their string representations from generic class names to meaningful syntax-based descriptions.

• Implements toString for Visibility to display pub or pub(path) instead of Visibility
• Implements toString for StructField to display field signatures like field: type or pub field: type
• Updates all test expectations to reflect the new string representations

Reviewed changes

Copilot reviewed 7 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
rust/ql/lib/codeql/rust/elements/internal/VisibilityImpl.qll	Implements toStringImpl and toAbbreviatedString for Visibility to render as pub or pub(path)
rust/ql/lib/codeql/rust/elements/internal/StructFieldImpl.qll	Implements toStringImpl for StructField to render field signatures with optional visibility, name, and type
rust/ql/.gitattributes	Removes VisibilityImpl.qll from linguist-generated list since it's now hand-modified
rust/ql/.generated.list	Removes VisibilityImpl.qll from the generated files list
rust/ql/test/extractor-tests/utf8/ast.expected	Updates test expectations for Visibility and StructField toString output
rust/ql/test/extractor-tests/macro-in-library/PrintAst.expected	Updates test expectations for Visibility toString output
rust/ql/test/extractor-tests/macro-expansion/PrintAst.expected	Updates test expectations for Visibility and StructField toString output
rust/ql/test/extractor-tests/generated/Visibility/Visibility.expected	Updates test expectations for Visibility instances
rust/ql/test/extractor-tests/generated/Trait/Trait.expected	Updates test expectations for Visibility in trait declarations
rust/ql/test/extractor-tests/generated/StructFieldList/StructFieldList.expected	Updates test expectations for StructField instances in field lists
rust/ql/test/extractor-tests/generated/StructField/StructField.expected	Updates test expectations for StructField instances
rust/ql/test/extractor-tests/generated/Module/Module.expected	Updates test expectations for Visibility in module declarations
rust/ql/test/extractor-tests/generated/MacroDef/MacroDef.expected	Updates test expectations for Visibility in macro definitions

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