2D spherical geometry

We want to add 2D spherical geometry $(r, \theta)$ on the grid with axisymmetry in $\phi$.

The following tasks need to be done:

• update the geometry source terms in Castro/Source/sources/Castro_geom.cpp to have the geometric terms (done in https://github.com/AMReX-Astro/Castro/pull/2955)
• add the primitive variable source terms (perhaps via #2473) and ensure that d/dtheta has 1/r in interface prediction (done in #2964)
• make sure that the geometry terms are included in the transverse flux correction functions (done in https://github.com/AMReX-Astro/Castro/pull/2961)
• add the geometry factors to diffusion (added in https://github.com/AMReX-Astro/Castro/pull/3048 and further verified in https://github.com/AMReX-Astro/Castro/pull/3054)
• update artifical viscosity (done in https://github.com/AMReX-Astro/Castro/pull/2954)
• update the shock detection algorithm (done in https://github.com/AMReX-Astro/Castro/pull/2959)
• add the correct cross product for the Coriolis force in the rotational source term (done in #2967)
• update AMReX to know about the area and volume factors (done in https://github.com/AMReX-Codes/amrex/pull/4141)
• make constant gravity work in the radial direction (done in https://github.com/AMReX-Astro/Castro/pull/2957)
• update our local area and volume functions (in Castro_util.H) to have the same factors (done in https://github.com/AMReX-Astro/Castro/pull/2953)
• address mom_flux_has_p (done in https://github.com/AMReX-Astro/Castro/pull/2958)
• add a ptheta flux register analogous to the pradial one (done in https://github.com/AMReX-Astro/Castro/pull/2960)
• make sure that the interpolation in AMReX uses the edge volume weights (these were inlined--see discussion in https://github.com/AMReX-Codes/amrex/pull/4141)(Done in https://github.com/AMReX-Codes/amrex/pull/4441)
• update the timestep computation (to use r dtheta) (done in https://github.com/AMReX-Astro/Castro/pull/2962)