carp_virtual_ip() and its state table are CARP protocol knowledge; under the
agreed structure (PR #37, docs/STRUCTURE.md) the base package carries only
contracts, data shapes and I/O-free reconcilers. They move to the driver that
speaks CARP (napalm-opnsense). The contract stays: VirtualIpsDict.carp and
VirtualIpDict.holds.
Nothing used the helper yet; it was released in 4.10.0 an hour ago.
netOrk #1121.