Decentralization client: Rebroadcast via a different node

[mkysel]

Is your feature request related to a problem?

If a message can be uniquely identified (such as a hash of the encrypted payload), if the message gets rebroadcast via multiple nodes, the client should be able to deduplicate these even if they have different node/sequenceIDs.

This relates to xmtp/xmtpd#431 and might become slightly simpler on the client.

Rebroadcasting via multiple nodes can also serve as a useful censorship resistant algorithm.

It seems that if a node becomes unavailable but the client has already signed the message, there is a lot of work that needs to be done to re-create the message with a different nodeId.