Merge DraggableList implementations

[bradenmacdonald]

This repo has two very similar implementations of DraggableList:

1. https://github.com/openedx/frontend-app-authoring/blob/fdf98a140/src/generic/DraggableList/DraggableList.jsx
2. https://github.com/openedx/frontend-app-authoring/blob/fdf98a140/src/course-outline/drag-helper/DraggableList.tsx

The historic reason is that component 1 was part of the editors code, which used to be a separate repo. Now that the editors live in the same repo, there are quite a few redundancies like this.

If possible, they should be merged into a single DraggableList component that works for all the use cases currently covered by both. Make sure the final result uses TypeScript and has no console warnings.

[bradenmacdonald]

@navinkarkera FYI.

[navinkarkera]

@bradenmacdonald The course-outline DraggableList is specific to Course outline and is rather complicated to be merged into the generic one, so I moved it under course-outline folder. On the other hand, the generic DraggableList is used in two or more places if I am not wrong.

[bradenmacdonald]

@navinkarkera It seems that they evolved from the same original code, so I was wondering if they can be combined again. If not, that's totally fine, but there's no documentation or anything explaining their different roles and how they're used. At the very least they should each get a large JSDoc explanation added.

The messages files are totally identical and could be combined.

[navinkarkera]

@bradenmacdonald Yes, I agree that we need to add some docs.