Add `--ci` mode to `uv cache prune` (#5391)
## Summary
Users can now run `uv cache prune --ci` (open to feedback on the name of
that flag) to remove all pre-built wheels from the cache, leaving behind
zipped, built wheels (which tend to be the most expensive assets to
re-create). This should greatly increase cache performance in CI
environments, since uploading unzipped wheels can actually hurt
performance if you're persisting the uv cache.
Closes https://github.com/astral-sh/uv/issues/5282.
