Investigate using a community maintained progress bar

[rbtcollins]

Describe the problem you are trying to solve
Stop us playing whack-a-mole with progress bars. Also get nicer, shinier ones. #1826 is perhaps a case of this (but perhaps also is just in the term detection bucket).

Describe the solution you'd like
Use https://github.com/mitsuhiko/indicatif

Notes
Some care is needed in investigating the behaviours involved but I think overall we could shrink rustup's code a bit, as well as directing effort on corner case configurations to a more central place, rather than the leaf node that rustup is.

[rbtcollins]

@mitsuhiko

[mitsuhiko]

I would love to get people on board to improve indicatif :)

[kinnison]

I think that switching to indicatif or another similar library would be an interesting approach. It'd be a significant departure for the current UI if we also funnelled all messaging through such a beast, so we'd need to think carefully.