[FEATURE] CLI color mode config

[brandonbloom]

Is your feature request related to a problem? Please describe.

ANSCI color codes are not supported in some situations (like various CI tools). If exo is to be used in these contexts, we need to make sure out output is plain-text friendly.

Docker Compose has an --ansi MODE flag, and many other tools, such as Git, have similar config values:

[color]
ui = auto # or false, or always

Describe the solution you'd like

Right now, we implement always, we should (1) implement both the auto and never codepaths and then (2) default to auto and (3) expose the config.

Describe alternatives you've considered

I've considered just doing (1) and (2), but not (3). It's not clear to me if/when anyone would actually want anything other than auto or always. And it's not clear to me if always makes sense in a global config (though never potentially makes sense in a global config?)

Overall, we should probably wait for feedback/use-cases for never and non-always.

[brandonbloom]

A related / more-general issue here is use of PTY features. I noticed that in the E2E tests, the logs are pretty ugly and verbose because they simply reprint the entire job/task tree on each status update during asynchronous tasks such as starting processes.