"RandomVectorGenerator" is-a "Supplier<double[]>"

RandomVectorGenerator does not bring any added value from the POV of the API users (as is now Commons Math).
For example, in class BaseMultiStartMultivariateOptimizer (package o.a.c.math4.legacy.optim), the RandomVectorGenerator constructor's argument can be replaced by Supplier<double[]> without loss of semantics. [It even provides greater generality.]