Find dependencies in VTKmConfig.cmake
VTK-m currently tries to create its own imported targets for external packages. This does not work in VTK because VTK intends to test things in different directories than is available when being built. This means that the locations found at build time are not useful at find_package() for install time and cannot be exported as LOCATION settings on the IMPORTED targets like vtkm::tbb. Instead, VTK-m should provide INTERFACE targets which chain to IMPORTED targets found at find_package(VTKm) time. VTK-m can ship its Find modules as needed.