Rename ${{step_dir}} to ${{func_dir}} for GitLab Functions compatibility

Summary

Rename the ${{step_dir}} syntax to ${{func_dir}} to align with the GitLab CI Steps → GitLab CI/CD Functions renaming initiative.

Details

GitLab CI Steps has been renamed to GitLab CI/CD Functions. For backwards compatibility, both ${{step_dir}} and ${{func_dir}} should be supported.

Reference Documentation

• GitLab CI Steps Documentation
• Parent Epic: Rename CI Steps to GitLab CI/CD Functions

Acceptance Criteria

• ${{func_dir}} syntax is recognized and functional
• ${{step_dir}} continues to work for backwards compatibility
• Documentation is updated to reflect both syntax options
• Tests cover both syntax options