Fix Clippy warnings: type complexity, needless borrow, etc.

[strmfos]

Summary

• Refactored the r1cs_to_qap.rs return type from a large tuple into a QAPTuple<F> type alias (resolving Clippy’s type_complexity).
• Removed unnecessary references in calls to evaluate_constraint (fixing Clippy’s needless_borrow).
• Simplified Ok(...)? usage in lib.rs (resolving needless_question_mark).
• Either reduced function arguments or allowed clippy::too_many_arguments where needed, to silence that lint without breaking API.

Why

• These changes address Clippy warnings and maintain the codebase in a warning-free state under -D warnings.
• Improves readability (alias for large tuple) and ensures more idiomatic Rust usage (avoiding pointless references).

Testing

• Verified locally with cargo clippy --all -- -D warnings that no warnings remain.
• Confirmed code compiles and tests pass, ensuring no functional regressions.