Roboports: Read robot requests in network

[foxoftheasterisk]

TL;DR

Give roboports a circuit setting that reads the total number of robots requested by all roboports in the logistic network.

What?

With Factorio 2.0, roboports now have the ability to request a number of robots to remain "on standby" in the roboport. I want a way to get these requests into the circuit network by reading the total number of requested robots and/or the number of unfulfilled requests. (Not both at once, obviously.)

Why?

I intend to use large numbers of robot requests (but not the same amount in each roboport), and I want to make sure there are enough robots in the network to actually fulfill said requests (without adding excessive numbers of robots and overloading the network, as I've done in previous games). The most sensible way I see to do so is to compare the total number of requested robots to the number of actual robots to see if more robots should be added, but I can't do that without being able to access the requested robot counts in circuits.