Fix parameter naming in generated code to resolve linter warnings

[Losses]

Problem

The rinf package generates code that copied from this repository, but the generated code consistently produces linter warnings that make repository maintenance painful. Every time rinf executes code generation, it outputs code that triggers the following warnings:

The parameter name 'value' doesn't match the name 'len' in the overridden method.
Try changing the name to 'len'.dart[avoid_renaming_method_parameters]

The parameter name 'value' doesn't match the name 'index' in the overridden method.
Try changing the name to 'index'.dart[avoid_renaming_method_parameters]

Impact

• Developer Experience: These warnings appear repeatedly during development, creating noise in the linter output
• Maintenance Burden: Every code generation cycle reintroduces these warnings, making it difficult to maintain clean code standards

Changes

• Updated parameter names from value to len in methods where the overridden method expects len
• Updated parameter names from value to index in methods where the overridden method expects index
• Ensured consistency between method signatures and their overridden counterparts

Related to: cunarist/rinf#632 (comment)
Maintainer: @temeddix