This extracts the routing package to its own repository
(https://github.com/ipfs/go-ipfs-routing). History has
been preserved. The new module has been gx'ed and published.

Imports have been rewritten and re-ordered accordingly.

An internal dependency to go-ipfs/repo has been removed
by substituting it with the go-datastore.Batching interface.

License: MIT
Signed-off-by: Hector Sanjuan <hector@protocol.ai>