Refactor: Extract replaceIdentifierReferences and remove reliance on this in ASTCallbacks

[LalitNarayanYadav]

Addresses #8694

Changes:

• Extracted replaceIdentifierReferences from ASTCallbacks into a standalone helper function
• Removed reliance on this binding within ASTCallbacks
• Replaced all this.replaceIdentifierReferences(...) calls with direct function calls
• Updated internal callback references (e.g., BinaryExpression, AssignmentExpression) to use explicit ASTCallbacks references
• Removed the inline helper implementation from ASTCallbacks

This improves modularity and makes the code easier to reason about, while preserving existing behavior.

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Screenshots of the change:

N/A (non-visual refactor)

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PR Checklist

• npm run lint passes
• Inline reference is included / updated
• Unit tests are included / updated

[LalitNarayanYadav]

This is the first incremental refactor PR for #8694.

I’ve focused on extracting replaceIdentifierReferences out of ASTCallbacks and removing reliance on this binding, without changing any transformation logic.

The goal is to make the code easier to reason about and prepare for further cleanup in smaller, reviewable steps.

Next steps (planned incremental PRs):

• Deduplicate BinaryExpression / LogicalExpression handling
• Introduce a guarded callback wrapper to reduce repeated ancestor checks
• Extract shared helpers used in control flow transformations
• Add a high-level pipeline documentation block

Happy to adjust the approach based on feedback before proceeding further.