Ability to ignore some data model paths when running `RemoveHiddenData`

### Description

SSB frequently uses hidden components in a way we did not first consider when developing the `RemoveHiddenData` functionality. They prefill the data model with values and use always-hidden `Dropdown` components to show the label for an option in a `RepeatingGroup` table. This is possible because historically app-frontend have displayed values in the repeating group table even if the components inside are actually hidden (whoops).

This also means that the 'hidden' data is deleted when using `RemoveHiddenData`. We'll fix this in https://github.com/Altinn/app-lib-dotnet/issues/1157 by not actually "removing" hidden data, but actually only roll back user changes (and this not being a user change would mean we don't actually remove anything even though the component is hidden).

In the meantime, SSB wishes for functionality to ignore certain paths from being removed by `RemoveHiddenData`. This, of course, also includes paths in repeating groups (aka properties of objects in arrays).

### Additional Information

- https://github.com/Altinn/app-lib-dotnet/issues/1157
- https://github.com/Altinn/app-frontend-react/issues/1669

Start by locating the RemoveHiddenData implementation and read the related issue 1157, then review how issue 646 describes paths inside repeating-group arrays. Define how configured ignored paths should behave, and consider the app-frontend issue 1669 for context. Done means specified paths, including repeating-group object properties, are preserved when RemoveHiddenData runs.

Written by the indexing model from the issue text.