Feature request: future v3 changes

[qdm12]

• Remove ipv4 or ipv6 option since it's confusing. This is code breaking change due to the pkg/publicip packages, and removes a few options for the IP echo services
• Remove provider_ip, since it's rather unneeded since the public ip is already known by the program and it would be more reliable to send it ourselves (especially to prevent the registrar server to assume the wrong Ip version)
• Rename PUBLICIP* to PUBLICIP_ECHO_ for configuration keys