Model network size fluctuation in simulations

[masih]

The current simulation modeling uses a fixed number of network participants throughout a single simulation. However, in a real-world network, churn is a common phenomenon where the number of
participants in the network may vary over time as some join or leave the network.

To improve the realism and accuracy of our simulations, I propose enhancing the simulation package to permit network size fluctuation. This will allow us to model realistic scenarios where
nodes can dynamically join or leave the network, simulating real-world networks that experience churn.

[BigLep]

@masih : I have added this to MX: Priority and sequencing TBD since I'm assuming this isn't needed anytime between now and shortly after f3 activation. Let me know if that is wrong.