Speed up scenarios test by vendoring wheels to (#169)

The find links index previously did not contain wheels for all packages,
causing unnecessary nested builds.

Before:

```
Benchmark 1: cargo nextest run -E "binary_id(uv::pip_install_scenarios)"
  Time (mean ± σ):      3.434 s ±  0.181 s    [User: 38.863 s, System: 7.532 s]
  Range (min … max):    3.325 s …  3.643 s    3 runs
```

After:

```
Benchmark 1: cargo nextest run -E "binary_id(uv::pip_install_scenarios)"
  Time (mean ± σ):      1.762 s ±  0.028 s    [User: 26.403 s, System: 5.404 s]
  Range (min … max):    1.734 s …  1.790 s    3 runs
```