go-data-transfer integration

[hannahhoward]

Once Lightning Storm works as a transfer suite, we need to fully integrate go-data-transfer.

There are a couple of approaches here:

We can:

1. one data-transfer channel per peer using bitswap
2. one data-transfer channel per peer serving metadata (needs go-data-transfer Graphsync metadata transport #8)

Or:

1. one data transfer channel per peer in an overall lightning sessions

There are advantages and disadvantages to both approaches:

• the single channel approach allows the provider to treat the whole request as a single semantic transfer, meaning they can prepare the whole dag ahead as needed
• the dual channel approach provides significantly more flexible payment options

This ticket is non-trivial and will likely turn into more than one ticket as we get closer to implementation