Anelastic cutoff issues in Urca sims

[biboyd]

There appears to be some sort of perturbation that arises at the anelastic_cutoff_density. This grows and starts to limit the timestepping if the interior convection is relatively slow. Example slices of the density perturbation and resulting velocity:

The provided inputs and model file can replicate this for a 256^3
inputs_model.zip

I've tested this using pure MPI and MPI+OMP, with the same results.

[zingale]

this is also where the sponge is turning on, so I think there is a lot happening there. I can make it a bit better with:

maestro.use_linear_grav_in_beta0  = 1
maestro.use_delta_gamma1_term = 0

(the magvel drops by about 4x).

But I want to try fixing the different species_pred_types