Make it easier to load wheels from the local file system

# 🚀 feature request

### Relevant Rules

Possibly in `whl_library`, but more likely in `requirements.txt`

### Description

I had created a patched wheel that I wished to test with Bazel and rules_python *before* publishing it to our internal Artifactory package index. There was no easy way to accomplish this.

I eventually worked out that I could test my patched wheel by using [pip2pi](https://pypi.org/project/pip2pi/) to create a local package index on my filesystem, then adding `--index-url=/tmp/pypi/simple` to the beginning of my `requirements.txt`.

See [this writeup](https://github.com/georgevreilly/torch21?tab=readme-ov-file#using-the-patched-wheel-with-rules_python) for full details.

### Describe the solution you'd like

If you have a solution in mind, please describe it.

I think the easiest thing for users is if they can specify a file path in `requirements.txt`; e.g.,

```
sympy==1.12
./tmp/torch-2.1.0+stripe.5-cp38-cp38-manylinux1_x86_64.whl
triton==2.1.0
```

Pip allows this, after all.

### Describe alternatives you've considered

Have you considered any alternative solutions or workarounds?

Comienza leyendo el manejo de whl_library y requirements.txt en rules_python para seguir cómo se analizan y resuelven las entradas de dependencias. Comprueba si las pruebas existentes cubren las fuentes de paquetes locales; se considera terminado cuando las reglas de Bazel pueden consumir una ruta de wheel en requirements.txt sin requerir su publicación en un índice de paquetes externo.

Escrito por el modelo de indexación a partir del texto del issue.