to_matrix

[mfalt]

We seem to use to_matrix only in one location https://github.com/JuliaControl/ControlSystems.jl/blob/9e5a846d1ac7928a816e78d6b55ce0d4e634996e/src/types/StateSpace.jl#L53 Where we for example already fail if D=LinearAlgebra.I. Maybe we should actually have a version that explicitly takes in dimensions instead? Or maybe for the cases like https://github.com/JuliaControl/ControlSystems.jl/blob/6b5f7a084ff106ff449b8fde453fc83d2054cd6f/src/synthesis.jl#L99 we should simply have a function like scalar_to_matrix which does nothing unless its a scalar, and in that case returns a 1x1 matrix?