Store LW_d and SW_d somewhere for coupled bucket #1500
Description
Right now the bucket stores net radiation R_n in its cache. In the prescribed radiation case this is filled via a call to net_radiation!, and in the coupled case it's expected to be filled by the coupler.
The coupler recently changed to receive SW_d and LW_d individually from the atmosphere instead of a "net radiative flux", to calculate surface fluxes more correctly (see PR). However for the bucket we don't have anywhere to store SW_d and LW_d.
I would prefer to store them in the CoupledRadiativeFluxes, fill them in the coupler, and use the same net_radiation! function for prescribed and coupled radiation.