imr/compound: introduce variant<Ts...>
imr/compound: introduce variant<Ts...>

avikivity/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla,duarten/scylla,duarten/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla