feat(core): drop doc onto split view (#9487)

fix AF-2068, AF-2069, AF-1175, AF-2061, AF-2079, AF-2034, AF-2080, AF-1960, AF-2081

1. replace `dnd-kit` with `@atlaskit/pragmatic-drag-and-drop`
2. allow creating split views by drag & drop the following
   a. WorkbenchLinks (route links), like journals, trash, all docs
   b. doc refs
   c. tags/collection
3. style adjustments to split view
4. remove split view's feature flag and make it GA for electron

https://github.com/user-attachments/assets/6a3e4a25-faa2-4215-8eb0-983f44db6e8c

packages/frontend/component/src/ui/dnd/draggable.ts

@@ -71,7 +71,6 @@ export const useDraggable = <D extends DNDData = DNDData>(
 
   const context = useContext(DNDContext);
 
-  // eslint-disable-next-line react-hooks/exhaustive-deps
   const options = useMemo(() => {
     const opts = getOptions();