V2

[Nuhvi]

A breaking change that disrupts the API significantly.

The main purpose of this version is to support Pkarr V2. It does so returning an RpcTickReport struct from Rpc::tick, enabling receiving MutableItem in a loop, without blocking the client.

Similarly, a Relay might listen to incoming requests, respond with a cached SignedPacket, and/or query the Dht if it doesn't have it cached. This means a Relay can be queried through the UDP socket as an alternative to HTTP in a native environment. To help with that the Rpc now exposes request, response and error from the KrpcSocket.

Additionally, the following changes make the Mainline Dht and AsyncDht itself nicer to use.

1. Reuse the closest nodes between subsequent queries, making Get queries much faster.
2. Use fresh latest nodes from a Get query in the Put query, making it faster.
3. Because of (2.) Put methods only need one flume channel instead of two.
4. Get methods return Iterator and Stream from the Dht and AsyncDht respectively.