Remove unused macro 'DHCPV6_CLIENT_SERVER_MAX'
Add configuration 'CONFIG_DHCPV6_CLIENT_PFX_LEASE_MAX' to configuration group
This implements a client for DHCPv6 IA_PD (Identity Association for Prefix Delegation). Goal was to have a IETF-compliant alternative to UHCP. The implementation was based on RFC 8415.