Move CIVariablesHelper to CI namespace

What does this MR do?

Moves CIVariablesHelper to CI namespace

Part of #207480 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content