Implement distance for firewall

[Honigeintopf]

Solution Summary

1. Use the distance value to extend routing paths in the FRR configuration.
2. This will make sure that the same firewall handles both the request and response, preventing packet drops and improving network stability.

[Honigeintopf]

The firewall-controller and also the fcm runs in the mini-lab environment.

When printing the frr.conf inside /etc/frr/frr.conf, it shows that the set as-path prepend works properly.
Also deleting/adding a firewall updates the distance in the firewall-controller now that distance is also inside the frr.conf with set as path prepend.

Next step would be to check whether that functionality really works and if routing is going over the firewall that has less distance.