Support Jump-ODE models

[isaacsas]

Needs:

• MTK release with Support ODEs as equations in JumpSystem ModelingToolkit.jl#3181
• Tests

rn = @reaction_network begin
       @parameters λ
       k*V, 0 --> A
       @equations D(V) ~ λ*V
       @continuous_events begin
           [V ~ 2.0] => [V ~ V/2, A ~ rand()*A]
       end
end        
jinput = JumpInputs(rn, [:A => 0, :V => 1.0], (0.0, 10.0), [:k => 1.0, :λ => .2])
jprob = JumpProblem(jinput; rng)
sol = solve(jprob, Tsit5()) 
plot(sol, idxs = [:A, :V])

[isaacsas]

@TorkelE do you want to review? Otherwise I think I'm happy to merge and followup on doc type updates (and maybe adding more correctness tests too at some point).