Support IPNS over PubSub

[lidel]

Right now, someguy only resolves IPNS over Amino DHT.

Let's use this issue for discussing adding support for IPNS over PubSub as a secondary resolution method:

• https://specs.ipfs.tech/ipns/ipns-pubsub-router/

Why?

• Once we have this in someguy, our rainbow-based fleet will benefit from this (faster lookups / updates, additional resiliency), without having to run pubsub on each rainbow instance.
• We have an opportunity to create another useful public utility (ipns cache and reprovider).

Prior Art

Kubo has opt-in support for resolving IPNS over PubSub (in addition to Amino DHT):

• https://github.com/ipfs/kubo/blob/master/docs/config.md#ipnsusepubsub
• https://github.com/ipfs/kubo/blob/master/docs/experimental-features.md#ipns-pubsub

IPNS over PubSub is enabled by default in IPFS Desktop and Brave,
but is not in Kubo because it lacks GC of unused topics, and it could cause trouble in server environments:

• Enable IPNS over pubsub by default  kubo#8591
• IPNS Pubsub Reprovider Duration (GC for unused topics) kubo#8586

Someguy is in the same spot: we need some sort of topic GC before we can enable pubsub router in someguy.