Summary of the charges in a transaction.
Storage is charged independently of computation.
There are 3 parts to the storage charges:
storage_cost: it is the charge of storage at the time the transaction
is executed. The cost of storage is the number of
bytes of the objects being mutated multiplied by a
variable storage cost per byte storage_rebate: this is the amount
a user gets back when manipulating an object. The
storage_rebate is the storage_cost for an object minus fees.
non_refundable_storage_fee: not all the value of the object storage
cost is given back to user and there
is a small fraction that is kept by
the system. This value tracks that charge.