[API] Show computation costs to StructLog transaction trace

[hyunsooda]

Proposed changes

Added two fields, computationCostTotal and computationCostUsed in debug.trace* APIs.

> debug.traceTransaction("0x58c1096e91560a0aae81332241168d1515729d29098e6899dcb22804ef1635a9")
{
  failed: false,
  gas: 21546,
  returnValue: "000000000000000000000000000000000000000000000000000000000000007b",
  structLogs: [{
      computationCostTotal: 150000000,
      computationCostUsed: 120,
      gas: 146,
      gasCost: 3,
      ...
  }, {
      computationCostTotal: 150000000,
      computationCostUsed: 310,
      gas: 143,
      gasCost: 3,
      memory: [],
      op: "DUP1",
      ...
  }, 
  ...

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Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[hyunsooda]

@blukat29,

Consider removing the Computation field from the StructLog struct to reduce its size. This value can be derived within the loop as ComputationCostLimit - OpcodeCC. Let me know if this approach is acceptable.

[blukat29]

@hyunsooda But the computation field is not Limit - opcodeCC, it's ComputationCostLimit - ComputationCostSum. It's inconvenient to sum up all opcodeCCs from the trace.

[hyunsooda]

The calculation is equivalent to accumulating from the limit to each step's opcode CC, and this can be accomplished simply by

+ sum := cc
   for index, trace := range logs {
      if logTimeout {
          return nil, fmt.Errorf("trace logger timeout")
      }
+     sum -= trace.ComputationCost
      formatted[index] = StructLogRes{

Initially, I hesitated to implement this change, fearing it might compromise readability. However, I highlighted its value considering the memory-saving benefits, contingent on the number of StructLog instances instantiated.