Allow users to modify 'bucketMaxSpanSeconds' and 'bucketRoundingSeconds' directly via collMod. As for create, we want to enforce that both values are strictly positive and that 'bucketRoundingSeconds' is no greater than 'bucketMaxSpanSeconds', and we will enforce that a collection cannot have 'granularity' set unless it corresponds perfectly with the set values for the other two parameters.

When the user changes these two values, the values are not allowed to decrease.