Refactor SubscribeTransactionStatus

[rodrigo-pino]

SubscribeTransactionStatus function, in the rpc package is a huge function (not adding any links because the package is going through heavy refactoring).

It is a complex function which holds in itself the definition of another complex function. The inner function should be re-factored apart and be defined externally.

[TheRanomial]

I’d like to resolve this.