dns: Report all transport errors in a dial attempt

[elenaf9]

Description

One dns address can be resolved recursively to multiple IP addresses.
When resolving a dns address, our dns transports tries to dial all the resulting IP addresses through its inner transport and returns an error once the last pending dial attempt failed.

The returned error is the error from the last dial attempt. Errors from earlier attempts are only logged, but not returned to the user.
This can be problematic because the info about why the other dialing attempts failed is lost, resulting in issues like #5871 where a handshake fails without the user being notified of it.
Instead of only returning the error from the last dial attempt, I think we should return all errors similar to how it's done on the swarm level with DialError::Transport.

Motivation

One of the currently hidden dial errors may include crucial information, like the "cargo feature rsa is not enabled" info that the user was missing in #5871.

Current Implementation

Only the error from the last dial attempt is logged.

Are you planning to do it yourself in a pull request?

Maybe

[rose2221]

i would like to work on it!

[elenaf9]

i would like to work on it!

Great, thank you! Let me know if you need any help.