fix: filter public ips

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What does this fix?

This fixes a regression introduced with the cached router.

Because the cachedRouter was wrapping sanitizeRouter, any providers that has no addresses, were thus getting populated straight from cache without going through sanitizeRouter.

This resulted in us returning providers with private IPs.

How does this fix

This PR ensures that whatever the cached router spews out, gets properly sanitised.

Open question

• sanitizeRouter removes private IPs, but it doesn't remove records that have no IPs. In theory, there's might be an edge case where we find records that only contain private IPs, that are then removed by sanitizeRouter, leading frontends/consumers of this to issue a subsequent calls. This seems pretty unlikely.
  • Is it even possible for would a peer show up in dht.FindPeer with only private IPs (if you're connecting to Amino)?
  • We can also make sure of this by adding a filter in the sanitizeRouter, but it seems like this might be unnecessary work.