refactor: migrate avoid_unused_parameters

[andrew-bekhiet-solid]

removes LintCodeCopyWith so the tests can compile, can be re-added later
improves code comments
adds FakeAnalysisOptionsLoader to help in testing

[gemini-code-assist]

Code Review

This pull request refactors the avoid_unused_parameters lint rule to align with the new SolidLintRule API, replacing custom lint builder APIs with RuleVisitorRegistry and RuleContext. It also introduces comprehensive unit tests and a fake analysis options loader for testing. Feedback on the changes highlights a potential issue in visitFunctionExpression where anonymous functions defined inside excluded methods or constructors are not correctly ignored, which could lead to false positives. A suggestion was provided to check for any enclosing executable declaration to resolve this.

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