Inclusion check with non-convex sets in hybrid solve

[mforets]

Consider the hybrid solve when we check if the newly computed set has already been explored:

                # check if this location has already been explored;
                # if it is not the case, add it to the waiting list
                r = target(H, t)
                Xr = StateInLocation(X, r)
                if (count_jumps <= max_jumps) && !(Xr ⊆ explored_list)
                    push!(waiting_list, tprev, Xr)
                end

Here it may happen that Xr is not contained in any particular element of explored_list, but however it is contained in the union of some explored sets, as in the picture below. Idea: can we test for inclusion between pairs of elements? This may help to more easily find fixpoints.