* swarm/network/stream: disambiguate chunk delivery messages (retrieval vs syncing)
* swarm/network/stream: addressed PR comments
* swarm/network/stream: stream protocol version change due to new message types in this PR
* swarm/network/stream: generalize SetNextBatch and add Server SessionIndex
* swarm/network/stream: fix a typo in comment
* swarm/network/stream: remove live argument from NewSwarmSyncerServer