Add CI_PROJECT_DIR to list of available variables

What does this MR do and why?

Adds CI_PROJECT_DIR to list of variables available to test container

MR acceptance checklist

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

• Commits include Changelog: trailer
• I have evaluated the MR acceptance checklist for this MR.