Rollout the "/include repository" and "/include directory" features

What does this MR do and why?

This fully rolls out the /include repository and /include directory features on Duo Chat.

The duo_include_context_repository is already enabled globally on production: #540543 (comment 2911067374).

References

• Epic: Duo Chat Integration - IDE (gitlab-org#17300 - closed)
• Rollout issue: [FF] `duo_include_context_repository` -- (#540543 - closed)

Screenshots or screen recordings

/include repository and /include directory features on VsCode Duo Chat:

List of available include contexts	Include repository	Include directory

How to set up and validate locally

1. On VsCode, connect to your local Gitlab instance
2. Make sure you have the GitLab Workflow extension installed
3. Go to the Duo Chat panel, and start typing /include on the chat box
4. Verify that the "Repositories" and "Directories" options exist

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #540543 (closed)