Show method for HydrostaticFreeSurfaceModel summarizes advection schemes

[navidcy]

Closes #3197

julia> using Oceananigans

julia> grid = RectilinearGrid(size=(2, 2, 2), extent=(1, 1, 1))
2×2×2 RectilinearGrid{Float64, Periodic, Periodic, Bounded} on CPU with 3×3×3 halo
├── Periodic x ∈ [0.0, 1.0)  regularly spaced with Δx=0.5
├── Periodic y ∈ [0.0, 1.0)  regularly spaced with Δy=0.5
└── Bounded  z ∈ [-1.0, 0.0] regularly spaced with Δz=0.5

julia> model = HydrostaticFreeSurfaceModel(; grid, momentum_advection=nothing, tracer_advection=nothing, tracers=nothing, buoyancy=nothing)
HydrostaticFreeSurfaceModel{CPU, RectilinearGrid}(time = 0 seconds, iteration = 0)
├── grid: 2×2×2 RectilinearGrid{Float64, Periodic, Periodic, Bounded} on CPU with 3×3×3 halo
├── timestepper: QuasiAdamsBashforth2TimeStepper
├── tracers: ()
├── closure: Nothing
├── buoyancy: Nothing
├── free surface: ImplicitFreeSurface with gravitational acceleration 9.80665 m s⁻²
│   └── solver: FFTImplicitFreeSurfaceSolver
├── advection scheme:
│   └── momentum: Nothing
└── coriolis: Nothing

julia> model = HydrostaticFreeSurfaceModel(; grid)
HydrostaticFreeSurfaceModel{CPU, RectilinearGrid}(time = 0 seconds, iteration = 0)
├── grid: 2×2×2 RectilinearGrid{Float64, Periodic, Periodic, Bounded} on CPU with 3×3×3 halo
├── timestepper: QuasiAdamsBashforth2TimeStepper
├── tracers: (T, S)
├── closure: Nothing
├── buoyancy: SeawaterBuoyancy with g=9.80665 and LinearEquationOfState(thermal_expansion=0.000167, haline_contraction=0.00078) with ĝ = NegativeZDirection()
├── free surface: ImplicitFreeSurface with gravitational acceleration 9.80665 m s⁻²
│   └── solver: FFTImplicitFreeSurfaceSolver
├── advection scheme:
│   ├── momentum: Centered reconstruction order 2
│   ├── T: Centered reconstruction order 2
│   └── S: Centered reconstruction order 2
└── coriolis: Nothing

[francispoulin]

I am so glad you did this. It's very helpful!

[francispoulin]

Looks good and a step forward!