calculate operation cost only once

[ayrat555]

Currently, we're calculating operation cost two twice, the first time in Functions.not_enough_gas?, the second time when subtracting the cost in machine state.

The cost operation in top 20 most used operation in EVM

'Elixir.EVM.Gas':cost_with_status/2                                                     442309     0.34    131917  [      0.30]
'Elixir.EVM.Gas':operation_cost/4                                                       442309     0.38    145659  [      0.33]
'Elixir.EVM.Gas':memory_cost/3                                                          442309     0.42    161097  [      0.36]
'Elixir.Decimal':div_calc/5                                                             923353     0.54    210818  [      0.23]
'Elixir.Access':get/3                                                                   909342     0.60    230840  [      0.25]
'Elixir.EVM.Operation':metadata/1                                                      1769202     0.79    303990  [      0.17]
'Elixir.EVM.MachineCode':current_operation/2                                           1105747     0.80    309092  [      0.28]
'Elixir.EVM.Operation':inputs/2                                                        1105764     0.87    335668  [      0.30]
'Elixir.EVM.Stack':pop_n/2                                                             3119325     1.94    750072  [      0.24]
'Elixir.Macro':do_camelize/1                                                           3004991     2.06    797937  [      0.27]
'Elixir.EVM.MachineCode':do_valid_jump_destinations/2                                 16059398     4.67   1809400  [      0.11]
binary:at/2                                                                           17381808     4.96   1921120  [      0.11]
'Elixir.EVM.Operation':encode/1                                                       16280544     8.73   3380107  [      0.21]
'Elixir.EVM.Operation':decode/1                                                       16059398     8.98   3475724  [      0.22]
'Elixir.EVM.Operation':push_length/1                                                  16059398     9.16   3548780  [      0.22]
'Elixir.EVM.Operation':next_instr_pos/2                                               16059398     9.34   3616411  [      0.23]
'Elixir.Map':get/2                                                                    34351430     9.36   3625938  [      0.11]
'Elixir.EVM.Operation':get_operation_at/2                                             17386308    10.07   3899674  [      0.22]
'Elixir.Map':get/3                                                                    34351541    11.84   4585781  [      0.13]

related to #557