Peer storage doesn't scale

[morehouse]

If SCBs get larger than 64KB, the peer_storage message sent to peers gets truncated. This means that later when the SCB is sent back in the your_peer_storage message, it fails the MAC check.

Based on typical scb_chan serialized sizes, peer storage starts to break at ~500 channels. At maximum scb_chan serialized sizes, things break at ~200 channels.

One potential solution is to packetize large SCBs for transfer to/from peers.