Scalar Multiplicity Vector

[jeremylt]

          Yeah, it is. But the important part is that is results in 1 scalar per node rather than 1 scalar per component per node (which is what `CeedElemRestrictionGetMultiplicity` gives out). So if there's an easy *Edit: and robust* way of getting out the components that correspond to a single component, then we could just do that and invert that vector.

Originally posted by @jrwrigh in #1223 (comment)

Local node multiplicity is the same across all components - we could save memory movement by letting a ElemRestriction provide a scalar multiplicity vector.