Create ViewComponent for DuoEnterprise Trials selection form

DuoEnterprise trial lead form logic is currently scattered across the controller and view layers, reducing maintainability.

As part of our broader initiative to make trial views more modular, we want to convert this form to use ViewComponents.

• Convert the DuoEnterprise trial selection form to use ViewComponents
• Improve testability through component isolation
• Maintain consistency with the patterns established in Ultimate trials - see 505669
• Associated MR