Simulate ridge regression parameters.
- N: Prior precision times mean for weights, where each column represents the mean of the weight for a separate output.
- Λ: Common prior precision.
- α: Common prior weight and likelihood covariance shape.
- β: Prior covariance scale accumulators.
Returns: Matrix of weights and vector of variances, where each column in the matrix and element in the vector corresponds to a different output in the regression.