evaluate the performance change for storage accesses when accessing small vs large values

[nagisa]

Description

In memtries only the relatively small values are held in-line, whereas the larger ones need to be fetched from the underlying storage. There is currently no cache for these values, other than what rocksdb itself may have. So the performance characteristics between these two types of accesses may be very different.

It may make sense to have two different gas fees for these two different types of accesses, depending on how much difference there really is.

cc @akhi3030 @shreyan-gupta