AddCat Bitswap Integration Tests

* adds delay/latency configuration to the `datastore`, `Bitswap.VirtualNetwork`, and `mockrouting` types.
* adds benchmarks to observe the effect that (each type of) latency has on AddCat performance.
* adds long-running integration tests. execute with env variable `IPFS_EPIC_TEST`

Still playing around with variables.

nice-to-have: mock out the network at a lower layer

I hereby dedicate this PR to Riff Raff. https://www.youtube.com/watch?v=TL0RqEsF_mY