Refactor task list to only show one task at a time

[acburdine]

After the ES6 refactor, the most complex CLI commands were refactored to use listr - a pretty awesome module for rendering task lists with statuses, as well as cleaning up a lot of the promise chaining behavior.

However, the current rendering module it uses by default (this one) can have UX issues when on a slow terminal connection (e.g. SSH connections to servers overseas). Basically because it renders (and re-renders) the entire task list every cycle, it can sometimes appear to be "flashing", e.g. noticeably disappearing and then reappearing, which isn't super great for UX.

I will open an issue on the relevant repository to see if there's willingness to implement this as a custom option; however if not then it will need to be manually implemented here.

Could be important, because of prompts to the user!