MDL-40975 ActionMenu: Add support for fillers in primary menus

This is required to maintain horizontal alignment of primary menus in rows.
MDL-40975 Course: Take activity drag handle out of nested span
MDL-40975 Course: Print a filler when groups mode is not supported but editing is enabled
MDL-40975 Course: Make the completion tracking look the same as other icons when editing
MDL-40975 Course: Move all editing icons to the end of the line
MDL-40975 Course: Move the spinner some more
MDL-40975 Course: Move activity text back to bottom alignment with images