WIP: Ticket40041: refactor connection/channel description code

Tons and tons of our code used connection->address and addr directly for logging. That's not so good, since we want to refactor their users, and simplify the real_addr/canonical_addr code.

This branch adds a pair of connection_describe_peer() and connection_describe() functions that we can use to make our logging cleaner. It also simplifies the channel description code, and clarifies the guarantees that its functions make.

Closes #40041 (closed)