MueLu: adding support for linear interpolation prolongation in region MG

Created by: lucbv

Enhancement

@trilinos/muelu

The current StructuredRegionDriver cannot run if the interpolation order used by GeometricInterpolationPFactory is equal to 1, only order 0 (piece-wise constant) can be used now. The idea is to modify how the coarse composite maps are constructed, technically if no coarse grid solve are required then the code should work with linear interpolation.