`AtmosphereModel.pressure` and `AtmosphereModel.pressure_solver` should probably be properties of `AnelasticFormulation`

[glwagner]

Breeze.jl/src/AtmosphereModels/atmosphere_model.jl

Lines 47 to 48 in 304f38a

	pressure :: Prs
	pressure_solver :: Sol

these properties should probably be in AnelasticFormulation.

First of all, "pressure" is actually the pressure perturbation (which participates in the velocity update):

Breeze.jl/src/AtmosphereModels/anelastic_formulation.jl

Lines 274 to 305 in 304f38a

	@kernel function _pressure_correct_momentum!(M, grid, Δt, αᵣ_pₙ, ρᵣ)
	i, j, k = @index(Global, NTuple)
	ρᶠ = ℑzᵃᵃᶠ(i, j, k, grid, ρᵣ)
	ρᶜ = @inbounds ρᵣ[i, j, k]
	@inbounds M.ρu[i, j, k] -= ρᶜ * Δt * ∂xᶠᶜᶜ(i, j, k, grid, αᵣ_pₙ)
	@inbounds M.ρv[i, j, k] -= ρᶜ * Δt * ∂yᶜᶠᶜ(i, j, k, grid, αᵣ_pₙ)
	@inbounds M.ρw[i, j, k] -= ρᶠ * Δt * ∂zᶜᶜᶠ(i, j, k, grid, αᵣ_pₙ)
	end
	"""
	$(TYPEDSIGNATURES)
	Update the predictor momentum ``(ρu, ρv, ρw)`` with the non-hydrostatic pressure via
	```math
	(\\rho\\boldsymbol{u})^{n+1} = (\\rho\\boldsymbol{u})^n - \\Delta t \\, \\rho_r \\boldsymbol{\\nabla} \\left( \\alpha_r p_{nh} \\right)
	```
	"""
	function make_pressure_correction!(model::AnelasticModel, Δt)
	launch!(model.architecture, model.grid, :xyz,
	_pressure_correct_momentum!,
	model.momentum,
	model.grid,
	Δt,
	model.pressure,
	model.formulation.reference_state.density)
	return nothing
	end

Also, we don't have a pressure perturbation or pressure solver for a FullyCompressibleFormulation.

Discussed with @kaiyuan-cheng

With a fully compressible formulation, we may not have pressure either --- for example we may prognose density or an Exner function, and then pressure would be computed on the fly from those variables.