Function eval_folded_constraints 

pub fn eval_folded_constraints<F, EF>(
    base_constraints: &[SymbolicExpression<F>],
    ext_constraints: &[SymbolicExpressionExt<F, EF>],
    constraint_layout: &ConstraintLayout,
    inputs: &[EF],
    layout: &InputLayout,
    periodic_values: &[EF],
) -> EF
where
    F: Field,
    EF: ExtensionField<F>,

Evaluate the folded constraint accumulator from symbolic constraints.

Merges base and extension constraints in evaluation order (using the ConstraintLayout), then folds them via Horner with alpha.