Add fix toggle support to the wp-cli commands #1676

I want to be able to turn on or off a fix using wp-cli. We have other commands already so this would follow the same pattern.

Fixes are defined following an interface that is easy to follow. Each fix has a slug and they all have a checkbox which stores an on or off value and I shold be able to toggle them with cli.

I should be able to list all fixes with the command too. If we have just the free plugin list only the free ones, if we have pro as well list the pro fixes too.