Document which address functions we should use, and when
nickm says that there are a lot of ways to get an address in Tor.
Let's document the functions that are left at the end of legacy/trac#23975 (moved), and when each of them should be used. It would be nice to have a summary, and then also details in each function comment.
We'll need to include these functions:
- node_get_*_*port()
- *_choose_address()
- any others?