♻️(frontend) Refactor DashboardItemOrder

[rlecellier]

Purpose

issue: https://github.com/openfun/richie/issues/2159

• [x] move DashboardItemOrder as sub-component of order's detail page: OrderDetails
• [ ] create a sub-component of order's listing page: OrderListItem
• [ ] extract order listing test from OrderDetails to pages/DashbaordCourses and pages/DashbaordCourses/components/OrderListItem
• [ ] extract order's details test from OrderDetails to pages/DashboardOrderLayout and pages/DashboardOrderLayout/components/OrderDetails
• [ ] factorize reused part of OrderListItem and OrderDetails into DashboardItem