Use infos from search engine instead of getting them again

Use infos from search engine instead of getting them again

When the search engine provides hits with GFileInfo, use that
to add the hits to the model directly, without going through
another round of async get_info calls.

To do this, we add a batched variant of the
_gtk_file_system_model_update_file call that takes lists of
GFiles and GFileInfos. Again, we can avoid repeated resorting
that happens when the files are updated individually.