fix: correct customizer typing in registerCustomAddresses

[bigint]

• Update customizer to use generic <T> with proper string | number | symbol key type
• Return undefined explicitly for compatibility with lodash mergeWith
• Ensures stricter type-safety when merging custom addresses, deployments, and unwrapped tokens

[Copilot]

Pull Request Overview

This PR improves type safety in the registerCustomAddresses function by replacing the loose any typing in the customizer function with proper generic types. The changes ensure stricter type checking when merging custom addresses, deployments, and unwrapped tokens.

• Replace any types with generic <T> type parameter for better type safety
• Add explicit void return type for lodash mergeWith compatibility
• Update parameter types to use T | undefined instead of any

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[Rubilmax]

The value of this type is not much but lgtm