Print dial status messages to stderr

[Stebalien]

Currently, it can be a bit difficult to debug dial errors because:

1. We only print the last error.
2. We don't clearly state what addresses we're trying to dial.

Printing something like,

error: ...
error: ...
dialing [3/N]: /ip4/STUFF...

would make this significantly easier to debug.

see #3933

[reinerRubin]

@Stebalien, I am going to try this one.

As I understand, if we want more informative final "failed to bootstrap" err, the bootstrap errs should not be just reduced to the last.

https://github.com/ipfs/go-ipfs/blob/8c96e3be90ac5ed4b34bb765833486f6b7816eaa/core/bootstrap.go#L196

upd
Yeah, it is more about go-libp2p-swarm/swarm_dial.go. Probably I'll do PR to that repo.

[Stebalien]

We now return all (or most) errors when we fail. However, we don't print dial progress. Ideally, we'd pass some kind of status channel through with the context. Alternatively, we could implement this once we have a proper event system in libp2p.