Avoid ANSI codes in debug! messages (#15843)
## Summary
I spent time trying to figure out how to support this but came up empty.
It _seems_ like maybe the `DefaultFields` implementation in
`tracing-subscriber` uses debug formatting for fields...? So if you have
a string with ANSI codes, they end up printing as unformatted values? I
even reverted all our custom formatting in `logging.rs` and saw the same
thing.
Closes https://github.com/astral-sh/uv/issues/15840.
