Adapt kernels to include backend #167
Description
Once trixi-framework/Trixi.jl#2590 has landed, we have to adapt some kernels to the new signature (essentially just add another argument backend). In particular:
- calc_volume_integral!
- prolong2interfaces!
- calc_interface_flux!
- calc_surface_integral!
- flux_differencing_kernel!
- apply_jacobian!