[WIP] [Feature] 14005 show costs attributes in overview tab

[``* `#14005` Show costs attributes in overview tab``](https://www.openproject.org/work_packages/14005)

The following points are still missing:
1. Remove ``:spent_time`` in [``work_packages_overview_attributes.rb``](https://github.com/finnlabs/openproject-costs/blob/feature/14005_show_costs_attributes_in_overview_tab/lib/open_project/costs/hooks/work_packages_overview_attributes.rb)
2. Add overall costs information including the currency to API v3
3. Add spent units (a list of sums and their units) to API v3