E2E: Add Orchestrated code_suggestions_spec

What does this MR do and why?

Relates to https://gitlab.com/gitlab-org/quality/quality-engineering/team-tasks/-/issues/2128

This MR updates qa/specs/features/ee/api/14_model_ops/code_suggestions_spec.rb to contain new contexts that will allow it to run for both SaaS and Self-managed environments.

The SaaS context will only run against Staging-Canary, Staging, Canary and Production, where the necessary setup has already been configured on these environments (same as the current code_suggestions_spec today).

The Self-managed context will only run in e2e-package-and-test pipelines within two new jobs named ai-gateway-sync-seat-link and ai-gateway-sync-service-token (added in this MR), which will use the new Test::Integration::AiGateway scenario added to gitlab-qa. The ai-gateway-sync-service-token job differs only in that it enables the use_sync_service_token_worker feature flag during setup.

Test pipelines:

• gitlab pipeline with orchestrated self-managed jobs: https://gitlab.com/gitlab-org/gitlab/-/pipelines/1112138145
• Staging job showing SaaS context passes as expected: https://ops.gitlab.net/gitlab-org/quality/staging/-/jobs/12268710

⚠ Important ⚠ This MR can only be merged after the following:

• gitlab-qa!1247 (merged) has been merged to gitlab-qa and a new version of the gitlab-qa gem has been released.
• !139861 (merged) has been merged to bump gitlab-qa to version 13.1.0 in the GitLab project

Screenshots or screen recordings

N/A

How to set up and validate locally

1. Check out this branch locally
2. Export the following env vars:

export GITLAB_LICENSE_MODE=test
export QA_EE_ACTIVATION_CODE=<value from 1Password>
export QA_SKIP_PULL=true

3. Build the QA image with

docker build -t gitlab/gitlab-ee-qa:your-custom-tag --file ./qa/Dockerfile ./

4. Tag the current nightly build for the corresponding GitLab image

docker tag gitlab/gitlab-ee:nightly gitlab/gitlab-ee:your-custom-tag

5. If !139861 (merged) has still not been merged, you may need to update your Gemfile and Gemfile.lock to bump gitlab-qa to version 13.1.0
6. Run the following from the qa directory:

gitlab-qa Test::Integration::AiGateway gitlab/gitlab-ee:your-custom-tag

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.