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?

Commencez par lire la gestion de whl_library et requirements.txt dans rules_python afin de suivre la manière dont les entrées de dépendances sont analysées et résolues. Vérifiez si les tests existants couvrent les sources de paquets locales ; le travail est terminé lorsqu’un chemin vers un wheel dans requirements.txt peut être consommé par les règles Bazel sans nécessiter de publication dans un index de paquets externe.

Rédigé par le modèle d'indexation à partir du texte de l'issue.