This allows Kubo to respond to the GetClosestPeers() http routing v1 endpoint
as spec'ed here: https://github.com/ipfs/specs/pull/476
It is based on work from https://github.com/ipfs/boxo/pull/1021
We let IpfsNode implmement the contentRouter.Client interface with the new
method. We use our DHTs to get the closest peers. We try to respect the
count/closerThan options here. We then trigger FindPeers lookups to fill-in
information about the peers (addresses) and return the result.
Tests are missing and will come up once discussions around the spec and the
boxo pr have settled.
23f1b59177