refactor: Workflow: change Step to integer, and put external command argument into vec

[DongzeHE]

Step's value changed from quoted integer to integer

Previously, the Step field of the command record fields is expected to be a quoted integer. Now, this is changed to integer without quote.

External command arguments are provided as a vector in order

Previously, we required the arguments of any external command record to be provided as a order,value pair. Now, they are required to be provided as a vector, as vector naturally are ordered.