`dnsname.SanitizeHostname` truncates a hostname to 63 characters. When
that label was already taken, resolveGivenName appended "-N" to the
full base, producing a 65+ character GivenName. Such a name is not a
valid DNS label, so the node cannot be rendered into its own netmap
or any peer's, and on PostgreSQL the varchar(63) given_name column
rejects the write.
Trim the base so base plus suffix fits in a DNS label and strip a
hyphen left at the cut. isAutoDerivedGivenName now compares against
the same bump, so a trimmed name still follows hostname changes
instead of being treated as an admin rename.
Igor Serganov
c6723fa103