Update APF to new interface

[FredericWantiez]

No description provided.

[charlesknipp]

Love seeing this PR back in the rotation.

Instead of changing the mutability of the filter, we could instead dispatch on an Auxiliary callback.

struct AuxiliaryWeightCallback{WT} <: AbstractCallback
    log_weights::Vector{WT}
end

where we can replace update_weights! with a post update callback

function (aux::AuxiliaryWeightCallback)(
    model, algo, iter, state, observation, ::PostUpdateCallback; kwargs...
)
    aux.log_weights = map(state.particles) do particle
        logeta(particle, model, iter, observation; kwargs...)
    end
    state.log_weights += aux.log_weights
    return nothing
end

and replace reset_weights! with a post resample callback

function (aux::AuxiliaryWeightCallback)(
    model, algo, iter, state, observation, ::PostResampleCallback; kwargs...
)
    state.log_weights = state.log_weights - aux.log_weights[state.ancestors]
    return nothing
end

I haven't figured out a good way to dispatch filter with this particular callback built in, but ideally I'd still like to keep the filter(rng, model, APF(N), data) syntax. Although I'm sure it's not that difficult.