E2E test: add SM duo chat scenario web ide

What does this MR do and why?

Resolves #468425 (closed)

Orchestrated test which utilises the ai-gateway in fake mode, to simulate a self-managed set-up. The test opens the web ide and sends a simple request to duo chat. It then asserts that the fake response is displayed.

Also ran the gitlab.com version of the test against staging here: https://ops.gitlab.net/gitlab-org/quality/staging/-/jobs/14432369#L1623

How to set up and validate locally

CHROME_DISABLE_DEV_SHM=true QA_IMAGE="registry.gitlab.com/gitlab-org/gitlab/gitlab-ee-qa:jmc-dc-web-ide-sm"  DOCKER_DEFAULT_PLATFORM=linux/amd64    GITLAB_LICENSE_MODE=test QA_EE_ACTIVATION_CODE= GITLAB_QA_ACCESS_TOKEN= bundle exec gitlab-qa Test::Integration::AiGateway EE