Each node keeps a registry of manually added nodes (through the
addnode parameter, rpc call or UI) but there are currently no
limits imposed on that usage, which is a bit sloppy and can lead
to situations where memory is being used for storing addresses
that are never connected to, because the maximum number of
connections used for addnode entries is hardcoded as 8. This
could prevent smaller systems that host nodes (like those
running on an ARM SoC) to optimally use the available memory.
This enhancement limits the addnode functionality as follows:
1. Whenever over 799 nodes are added to the registry, require
the user to remove an entry before a new one can be added
2. Disallow very large addresses (more than 256 characters).
This limit provides for at least 4 levels of subdomains as
specified under RFC1035.
See https://datatracker.ietf.org/doc/html/rfc1035#section-2.3.1
