Adapt code to follow new ODINN API

[JordiBolibar]

Following the design of the new API of ODINN, the 1D models should follow the new API described here: ODINN-SciML/ODINN.jl#82 (comment)

We should basically follow this example for a 2D SIA model:

include("iceflow_utils.jl")
include("SIA.jl")

# Abstract type as a parent type for Mass Balance models
abstract type IceflowModel end

###############################################
###### SHALLOW ICE APPROXIMATION MODELS #######
###############################################

# Subtype structure for Shallow Ice Approximation models
abstract type SIAmodel <: IceflowModel end

@kwdef mutable struct SIA2Dmodel <: SIAmodel
    A::Float64
    B::Matrix{Float64}
    S::Matrix{Float64}
    dSdx::Matrix{Float64}
    dSdy::Matrix{Float64}
    D::Matrix{Float64}
    dSdx_edges::Matrix{Float64}
    dSdy_edges::Matrix{Float64}
    ∇S::Matrix{Float64}
    Fx::Matrix{Float64}
    Fy::Matrix{Float64}
    Δx::Float64
    Δy::Float64
    Γ::Float64
end