Refactor to extract API interactions and reduce complexity

[mcmire]

At a glance, the updateSmartTransaction, confirmSmartTransaction, getFees, and submitSignedTransactions methods look fairly complex. We should see if we can extract the logic here to separate files to make this controller easier to understand and test.

We should also see if we can extract API interactions, especially the logic involved to normalize response data, to separate files, for the same reason.