Improve offline IPNS (record) support

Libp2p should have better offline/disconnected-network record support:

• On resolve, IPNS records should be cached locally. This will:
  • Help with streaming resolve. Peers searching for popular records will get back "best effort" results along the way. We still won't be able to stop the search early as these "best effort" copies of the records won't be updated but it can help.
  • Help with offline situations. If a node resolves a record while online, they'll continue to have a copy of that record when offline. It may not be up-to-date but it's better than nothing.
  • Help with resolving on a disconnected network. If a subset of nodes "become" the entire DHT, they'll have all the records they've resolved recently.
• Users should be allowed to publish DHT records while offline (or in a disconnected network). DHT rebalancing (to be implemented) should take care of moving these records to the right place at the end of the day.

Dependencies:

• https://github.com/libp2p/go-libp2p-kad-dht/pull/291. Introducing this would break IPNS at the moment as we don't properly complete the query.

Start by reviewing the dependency in go-libp2p-kad-dht PR 291 and the current IPNS resolve and publish flows. Define how locally cached records, streaming best-effort results, offline publishing, and disconnected-network behavior should interact. Done means the behavior works offline and online without breaking IPNS resolution.