Task: retry on subscribe failures

[orbitalturtle]

Description

Following up on #194, we should try to make LNDK a bit more resilient in the face of temporary, short-lived network errors, or LND restarts. Otherwise, if there's even just one short-lived error thrown, LNDK will just shut down. This means making sure to retry establishing a connection when subscribe_custom_messages or subscribe_peer_events return connection errors.

As @a-mpch mentioned, though, during this period it's possible we'll miss peer message events while we're waiting to reconnect, which can cause payment failures, etc. To get around the problem with missing peer events, we can call ListPeers to double-check if the OnionMessenger is totally synced up with LND.

[a-mpch]

I'll be working on this! :)