Add cpu_affinity to get_nodes output

[dopheide-esnet]

Potential Enhancement

After testing that setting cpu_affinity in the config now works (yay!) I think it would be useful for zeek-client to report that information in 'get-nodes' output. The downside would be potentially requiring the 'psutil' python library and I'm not sure if you want to do that.

import psutil
process = psutil.Process(p.pid)
affinity = process.cpu_affinity()