make shock tube and blast wave tests run for SRHD when using MDA AV

The key step was to adapt a 'covariant' regularization that looks like

\partial_t D + \partial_x f_D^x = - \partial_x ( \mu ( \partial_t - \partial_x ) D ),

where the time derivative on the RHS is new compared to previous attempts. We approximate \partial_t D by the - \partial_x f_D^x.

Note that this is not truely covariant, but (\partial_t - \partial_x) ( \mu ( \partial_t - \partial_x ) D) would be. Problem is that we don't know how to approximate the second time derivatives or the mixed time-space derivatives. But it works this way, so leave it for now.

This PR adds example parameter files that allow to reproduce the SRHD tests from https://arxiv.org/pdf/2202.08839.pdf. To run the blastwave2 test it was important to add correct the evolved variable tau whenever the energy density eps turned slightly negative, as suggested in https://arxiv.org/pdf/2005.01821.pdf III.A. What is interesting is that atm we don't need an atmosphere description, but that's probably because those tests do not examine low densities.

---

Side note: Realized that !75 (merged) promoted Mesh to a parameteric type and now most of the HRSC and TCI structs suffer from type instabilities. Need to fix this in a separate PR.

src/SRHD/initialdata.jl

@@ -430,7 +430,7 @@ function initialdata_hrsc!(env, P::Project, hrsc::Union{HRSC.EntropyViscosity,HR
 
   @unpack mu, cellmax_v = get_cell_variables(env.cache)
   @unpack max_v         = get_static_variables(env.cache)
-  @unpack D             = get_dynamic_variables(env.cache)
+  @unpack D, S, tau     = get_dynamic_variables(env.cache)
   dg1d.new_broadcast_volume!(maxspeed, P.equation, env.mesh)
   Npts, K = layout(env.mesh)
   mat_max_v = reshape(view(max_v, :), (Npts, K))
@@ -438,8 +438,8 @@ function initialdata_hrsc!(env, P::Project, hrsc::Union{HRSC.EntropyViscosity,HR
     cellmax_v[k] = maximum(view(mat_max_v, :, k))
   end
   HRSC.compute_viscosity!(
-      mu,
-      D, cellmax_v,
+      mu, deepcopy(mu),
+      (D,S,tau), cellmax_v,
       mda_hrsc.av)
 end