[Fixes #59725212] Fails to disassociate dataset from workspace when using the multi-select link

 - The BulkDestroyer was using processData: true when sending datasetIds to be destroyed in bulk, so $
 was encoding the json array (i.e. converting [] to %5d form) and rails failed to parse the json.
 - Now we won't let Backbone/$ process this data, so we'll JSON.stringify it ourselves when inserting it into data