Add a preview option `uv init --build-backend uv --preview` that uses
the uv build backend when generating the project. The uv build backend
is in preview, so the option is also guarded by preview and hidden from
the help message and docs.
For https://github.com/astral-sh/uv/issues/3957#issuecomment-2518757563
## Summary
These were moved as part of a broader refactor to create a single
integration test module. That "single integration test module" did
indeed have a big impact on compile times, which is great! But we aren't
seeing any benefit from moving these tests into their own files (despite
the claim in [this blog
post](https://matklad.github.io/2021/02/27/delete-cargo-integration-tests.html),
I see the same compilation pattern regardless of where the tests are
located). Plus, we don't have many of these, and same-file tests is such
a strong Rust convention.
## Summary
Resolves#8417
I've just begun learning procedural macros, so this PR is more of a
proof of concept. It's still a work in progress, and I welcome any
assistance or feedback.
As per
https://matklad.github.io/2021/02/27/delete-cargo-integration-tests.html
Before that, there were 91 separate integration tests binary.
(As discussed on Discord — I've done the `uv` crate, there's still a few
more commits coming before this is mergeable, and I want to see how it
performs in CI and locally).
Following #5869, the documentation has some less-than-helpful
suggestions to use `uv help python` for details — we should link to the
`uv python` section instead.
konsti