[boost] [container] small_flat_set and small_flat_map

Given that Boost.Container has a small_vector now, would a piece of work that changed flat_set and flat_map to use small_vector<0> internally be feasible? I ask because I feel like if this was the case it would be almost trivial to expose flat_tree<N> through small_flat_set<N> and small_flat_map<N> types to provide the small size optimisation for these two containers.