feat(duo-chat): add config files for staging-ref daily runs

What does this merge request do and why?

This MR add sconfig files for staging-ref daily runs. Staging Ref now has Duo Chat that is powered by self-hosted models. This configuration will run daily evaluations against Staging Ref.

We've enabled AI features powered by self-hosted models on the Staging Ref environment: Functional Testing: Configure self-hosted model... (gitlab-org/gitlab#497784 - closed). The final goal is to run evaluations against https://staging-ref.gitlab.com and get a nice dashboard like: https://lookerstudio.google.com/u/0/reporting/151b233a-d6ad-413a-9ebf-ea6efbf5387b/page/p_dt1c6y4xed.

Related issue: Build a dashboard with evaluations against Stag... (gitlab-org/gitlab#498463)