Make filters a regular step (#14586)

- Remove special design logic for filters and edge with filters
- Remove backend logic to delete filters along with parent steps
- Add filters to the node type picker



https://github.com/user-attachments/assets/5b6ceda4-d86f-48a3-8c93-37a885398a8d

packages/twenty-front/src/modules/workflow/workflow-variables/components/WorkflowVariablesDropdownStepItems.tsx

@@ -93,11 +93,10 @@ export const WorkflowVariablesDropdownStepItems = ({
         .includes(searchInputValue.toLowerCase())
     : true;
 
+  const objectLabel = displayedSubStepObjectMetadata?.labelSingular;
   const shouldDisplaySubStepObject =
     shouldDisplayRecordObjects && isObjectFoundThroughSearch;
 
-  const objectLabel = displayedSubStepObjectMetadata?.labelSingular;
-
   return (
     <DropdownContent widthInPixels={GenericDropdownContentWidth.ExtraLarge}>
       <DropdownMenuHeader