Sorter (reorderable list) - component that allows the user to specify/change order of subcomponents/content

### Description

Note: This issue was created in the design system repo. We thought there should be done some discusion if this could be solved in another way in Altinn 3 before we start making a component. [Original issue](https://github.com/digdir/designsystem/issues/847)

### Describe the component

The user are presented with a number of options or are tasked to add options themselves. Afterwards the user are allowed to change the order of the options presented (or added).

Example in one of our Altinn projects (Brukervennlige registertjenester, "lag nytt enkeltpersonsforetak" ) the user is tasked to selecting an main activity and 0-4 additional activites for their new business. It is very important that we know whatever activity is the main one listed first, but the user might want to change the order after they have selected/added up to 5 different activities. In this case, for each line inside this component there is one select-field and one button to remove the line.

### If you have any examples or similar components feel free to include links or screenshots here

Topic is discussed a bit here:
https://www.darins.page/articles/designing-a-reorderable-list-component

### Additional Information

_No response_

Start with the linked original issue and the discussion in the referenced reorderable-list article. First resolve whether this belongs in the design system or should be solved another way in Altinn 3; then define the component's ordering, adding, removal, and selection behavior. Done means the design decision and component scope are agreed before implementation.

Written by the indexing model from the issue text.