Replace Action monad with Cli monad

[mitchellwrosen]

Overview

Continuation of work on #3253

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This change is 

[pchiusano]

wow, an epic refactoring. looks a lot cleaner!

[mitchellwrosen]

What is wrap and why don't we want haddocks to show for it? I guess because it's an internal implementation detail?

The default implementation just prevents the line "Minimal complete definition: wrap" appearing in the haddocks. wrap itself isn't exported, because users don't write Label instances - the only two instances it will ever have are defined internally.