If a @PlanningVariable has no valueRangeRef it should look for all @ValueRangeProviders that have no valueRangeRef for which the ValueRange element type is assignable to the planning variable.

So @PlanningVariable animal will use @PlanningProvider List<Cat>,
but @PlanningVariable cat will NOT use @PlanningProvider List<Animal>.

If no value ranges are found, fail fast.