Allow Usage of Change Tracking To Enable Caching and Attaching of Related Entities From Multiuple Queries

[bbrandt]

Let me know if you think something like this would be useful.

Maybe something like this? Would likely blow up memory usage when many time values used?

public class TimeTravelCacheKeyFactory : IModelCacheKeyFactory
{
    public object Create(DbContext context)
    {
        if (TemporalQuery.TargetDateTime != null)
        {
            return (context.GetType(), TemporalQuery.TargetDateTime);
        }
        return context.GetType();
    }
}

https://docs.microsoft.com/en-us/ef/core/modeling/dynamic-model#imodelcachekeyfactory