ci(framework:skip) Add e2e test to test Docker images

[Robert-Steiner]

Issue

Description

This PR adds a new reusable workflow to run a simple e2e test in docker compose. This workflow ensures that our images are tested and we are not releasing broken images.

Test Execution:

• The test builds the base and binary images and tags them with the e2e-test tag.
• A new flwr NumPy example is created.
• The example is run using the complete with-TLS Docker Compose setup.
• The test passes when the run completes within 2 minutes.

Related issues/PRs

Proposal

Explanation

Checklist

• [ ] Implement proposed change
• [ ] Write tests
• [ ] Update documentation
• [ ] Make CI checks pass
• [ ] Ping maintainers on Slack (channel #contributions)

Any other comments?