Python downloads should show a progress bar

[konstin]

When downloading a python toolchain for running a tool, i wait several seconds without any output. This is very untypical and feels wrong for uv. We should add a message indicating the start of a large download and a progress bar. The message should be shown anyway since non-interactive environments don't show progress bars. (The video is from the failing https://github.com/astral-sh/uv/pull/4810, but it applies also when this is fixed)

Screencast from 2024-07-05 10-01-24.webm

[charliermarsh]

Agree!

[charliermarsh]

We already have infra for this from wheel downloads so I’ll label it as a good first issue.

[zanieb]

Oh there were some tracing progress bars in the uv-dev implementation but I guess we lost that. Big 👍 to adding progress bars here.