Apply column filters to the cell-output-display div itself

This will place the entirety of the output display in the margin

This should fix:
#6961

this does introduce an `outer par` bug in PDF output, which I will investigate separately.

src/resources/filters/layout/columns-preprocess.lua

@@ -84,7 +84,7 @@ function resolveColumnClassesForCodeCell(el)
               local custom_classes = float_classes[ref_type]
               local custom_caption_classes = float_caption_classes[ref_type]
               -- applyClasses(colClasses, captionClasses, containerEl, colEl, captionEl, scope)
-              applyClasses(custom_classes, custom_caption_classes, el, custom, custom, ref_type)
+              applyClasses(custom_classes, custom_caption_classes, el, childEl, custom, ref_type)
             else
               local figure = discoverFigure(figOrTableEl, false)
               if figure ~= nil then