Add native anonymity checkbox to every form

In GiveCampus giving forms, available controls depend on your permissions and the interface used by your institution.

Use the native anonymity control, not a generic checkbox with the same words. Legacy forms can render it within the name block, while newer forms expose a locked native Anonymous field. That explains why the existing checkbox may not be listed as an independent custom question. There is no universal bulk-add operation preserving the exact position across all form versions; support should inventory the forms and apply the supported version-specific setup.