This fixes three issues in addrman unserialization.
- An addrman entry can appear in up to 8 new table buckets. We store this entry->bucket indexing during shutdown so that on restart we can restore the entries to their correct buckets. Commit ec45646 broke the deserialization code so that each entry could only be put in up to one new bucket.
- Unserialization may result in an entry appearing in a 9th bucket. If the entry already appears in 8 buckets don't try to place it in another bucket.
- We unnecessarily rebucket when reading a peers.dat with file version 1. Don't do that.
This is a backport of core#20557