1. page list item are bound two draggables. adding `draggable` prop to WorkbenchLink to mitigate the issue.
2. DndService may not resolve datatransfer when dragging.
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
fix AF-1847
two issues:
1. original `dropTargetForExternal` only works if dragging target is from another window context. patched the library to bypass this issue
2. `dataTransfer`'s content is only available on `drop` event. This means we cannot have `canDrop` checks for external elements (like blocksuite links).
