Create a trafficlight client that is automated by the trafficlight server

[michaelkaye]

This PR should introduce a client for the trafficlight server. Nothing should run this code by default in any test automation.

Trafficlight is designed to coordinate and script multiple clients together to fulfil a simple test case end to end (eg, client -> server -> federated server -> client).

Checklist

• [ ] Tests written for new code (and old code if feasible)
  • N/A: this is inherently a test so no test required.
• [X] Linter and other CI checks pass
• [X] Sign-off given on the changes (see CONTRIBUTING.md)

Notes: Add trafficlight client using cypress.

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Here's what your changelog entry will look like:

✨ Features

• Add trafficlight client using cypress. (#9117). Contributed by @michaelkaye.

[michaelkaye]

I'm unsure whether the recent cypress test failures are real or not; There has been no change to the tests in question; other than /excluding/ the new trafficlight test from the testcases; this has a feeling of a flaky test somewhere.

[turt2live]

removing my review request - I don't think I can provide useful value beyond what's already been mentioned at the moment.

[michaelkaye]

Closing; this was factored away from the main matrix-react-sdk codebase and is now in matrix-org/trafficlight-adapter-element-web and has evolved since this branch.