`dance.search.selection` (and `smart`) strip out newlines

Steps to reproduce: Select multiple lines (i use `x` a few times with a helix keybinding) Use your keybinding for `dance.search.selection` (shift+8 by default) Press `/` to bring up the search input - it shows "no selections remain" Both helix and kakoune work (they treat the newlines as linefeed literals, though imo they should escape them as '\n')