resize! missing for MatrixOperator

[gaurav-arya]

Possibly should be modeled after https://github.com/SciML/OrdinaryDiffEq.jl/blob/21a5bbe8d844d889824f94d91948270567fa51d6/src/integrators/integrator_interface.jl#L250

[vpuri3]

resize is not defined for matrix op. it's only defined for function op and wrappers. it's not defined for abstract matrix either. so if you have a matrix op in there somewhere and you resize, it should error

[vpuri3]

in the link, J is usually a function op and supports resize functionality.

[vpuri3]

i think the link is just resizing of the concretized matrix.. this can be accomplished by first resizing and then concretizing. I don't think it needs a special method.