client/authority-discovery: Append PeerId to Multiaddr at most once (#6933)

* client/authority-discovery/worker: Extract address getter

* client/authority-discovery: Test for no duplicate p2p components

* client/authority-discovery: Append PeerId to Multiaddr at most once

When collecting the addresses to be published for the local node,
`addresses_to_publish` adds the local nodes `PeerId` to each
`Multiaddr`. Before doing so, ensure the `Multiaddr` does not already
contain one.

* client/authority-discovery: Remove explicit return