Fix output vsbuffer transfer via workspace edit.

[rebornix]

While playing Workspace Edit with notebooks, I found that when insert cells with outputs, outputs are always dropped. Turned out to be that we are not sending VSBuffer properly.

Notebook's execute handler will wrap the output updates with SerializableObjectWithBuffers to ensure that the buffers in outputs are serialized/deserialized correctly.

vscode/src/vs/workbench/api/common/extHostNotebookKernels.ts

Line 623 in 39df90b

return this._proxy.$updateExecution(this._handle, new SerializableObjectWithBuffers(updates));

Since we have notebook edits (which can contain output buffers) in WorkspaceEdit, we might want to do the same with MainThreadBulkEditsShape#$tryApplyWorkspaceEdit

cc @jrieken @mjbvz