true if valid, false otherwise.UriParser.isValidIPv6
bool isValidIPv6(string h) @safeValidate an IPv6 address literal.
Enforces RFC 3986 group counting: an embedded IPv4 tail counts as two h16 groups, an uncompressed address has exactly 8 groups, and a `::` compression must stand for at least one zero group (7 explicit at most). Lone leading/trailing colons and `:::` are rejected.
Parameters
h | IPv6 address string (no brackets, no zone id). |