One time test setup for the web-client's tests

We currently have a setup that runs the web-client's test in the CI. The tests are sharded and run with a matrix strategy. They currently take 30 minutes to run. Much of this time is spent setting up the context for running them. I think we can improve this using [a composite action](https://docs.github.com/en/actions/tutorials/create-actions/create-a-composite-action).

Look at the existing CI workflow for the web-client tests, likely in .github/workflows/. Understand the current matrix strategy and setup steps. Research GitHub composite actions to create a reusable setup action. The goal is to reduce the 30-minute runtime by caching or reusing the test context across shards.

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