Add some text decoration to toolchain CLI (#4882)
## Summary
Attempts to make the CLI output a little more consistent with the `pip`
interface. I opted to make the Python versions, requests, and filenames
blue, and the keys green, but open to opinions on that. (We use blue for
filenames elsewhere.)
Closes #4813.
Closes https://github.com/astral-sh/uv/issues/4814.
