Fixes: #18584 Add rack types column to manufacturers table

[renatoalmeidaoliveira]

Fixes: #18584 Add rack types column to manufacturers table

• Add Add racktype_count annotation to list view queryset
• create the LinkedCountColumn in ManufacturerTable

The result is the following image

Aditional Thougts:

• The issue makes the following statement:

Currently, users can assign manufacturers when creating rack types; however, there isn’t a straightforward way to view or filter these rack types by manufacturer within the interface.

• IMO only adding the Rack Types Collumn in the Manufacturer List View isn't enougth to solve the user issue.
• Looking at RackTypeFilterForm code the manufacturer_id field are defined but since it isn't referenced in any FieldSet the user are unable to select a Manufacturer to the filter.
• That's a really quick fix but sligtly outside the issue scope, so let me know if I should add the manufacturer_id field inside some filterset
• The Rack Type FilterSet seens the best option.