Add convective gustiness to (ocean) surface flux calculation

We're working on a way to modify the calculation of surface fluxes (over ocean first) to include the impacts of convective gustiness. A few years ago, @swrneale implemented the modifications needed to do this in a branch of CAM, which mostly involved modifications to a few cime scripts (`shr_flux_mod.F90` and `seq_flux_mct.F90`) to add a gustiness term to the calculation of the surface wind magnitude `vmag` based on an input convective precipitation estimate from CAM.

In the new CMEPS architecture, it seems this will involve modifying vmag in `cmeps/cesm/flux_atmocn/shr_flux_mod.F90` in the case where ocn_surface_flux_scheme=0. I suspect the (nearest?) equivalent to `seq_flux_mct.F90` is `cmeps/mediator/med_phases_aofluxes_mod.F90`, though I imagine a few other modifications might be necessary in `esmFldsExchange_cesm_mod.F90, fd_cesm.yaml` to pass the convective precipitation to the coupler.