fetch beacon entries from gossipsub

# Summary

See spike at https://github.com/ChainSafe/forest/issues/7364

Right now, when we need beacon entries, we query the https relay; we could avoid our reliance on that by using the dedicated gossipsub topic and feeding it into a cache.

We might also that would somehow resubscribe to the topic in case we don't get queries for longer period.

# Completion Criteria

- [ ] Feed beacon entries from gossipsub to the drand cache.
- [ ] Test that it works correctly, e.g., drop drand https relays and ensure recent queries to `MinerGetBaseInfo` work fine without it.
- [ ] Watchdog - if we don't get updates, we must resubscribe (workaround)
- [ ] Metrics around the new drand entries cache
- [ ] Metrics around the HTTP drand usage

# Additional Links & Resources