transport-manager: remove disconnected peers

[Imod7]

Rel: #268

Changes

• Added the disconnected_at timestamp to PeerState::Disconnected.
• Updated all the places where Disconnected is used by adding the new disconnected_at.
• Added an INTERVAL_DURATION of 60 minutes.
• In the next() method: added a tokio::time::interval with period equal to this duration and the ticker.
• Added the cleanup_disconnected_peers method which keeps the peers:
  • that were disconnected more recently than the cutoff
  • that are in all rest of the states such as Connected, Opening, Dialing.

Todos

• Add tests

[dmitry-markin]

Removing peers from transport-manager means we will never be able to connect to them.

[Imod7]

Removing peers from transport-manager means we will never be able to connect to them.

Ok, got it! So, I will close the PR for now. Also, thank you for all the feedback and insights shared through the chat!