[solidago] Update docstrings and add simple API for Pipeline

[amatissart]

Description

A first step before introducing mkdocs to build Solidago documentation.
Based on #1970

This branch introduces some new helpers to use the solidago pipeline:

• get_pipeline_objects() is replaced with get_pipeline_kwargs(criterion) and is generic for any TournesolInput
• pipeline.run(input, criterion) to avoid initializing the pipeline arguments manually

It makes running the pipeline easier than ever:

import logging

from solidago.pipeline import Pipeline
from solidago.pipeline.inputs import TournesolInputFromPublicDataset

logging.basicConfig(level=logging.INFO)

public_dataset = TournesolInputFromPublicDataset.download()
pipeline = Pipeline()

(users, voting_rights, user_models, global_model) = pipeline.run(
    input=public_dataset,
    criterion="largely_recommended",
)

---

Checklist

• I added the related issue(s) id in the related issues section (if any)
  • if not, delete the related issues section
• I described my changes and my decisions in the PR description
• I read the development guidelines of the CONTRIBUTING.md
• The tests pass and have been updated if relevant
• The code quality check pass

[lenhoanglnh]

Looks good to me.

[amatissart]

@lenhoanglnh Is it ok to merge this PR now into #1970 , or should we wait to avoid potential conflicts with your experiments on "neurips24"?