Updated visual consistency of lists and markdown task list rendering

Updated visual consistency of lists and markdown task list rendering

- Numbered and bullet list margins have been made consistent
   - Numbered lists margins were increase at some point to handle 3-digit
  numbers, Normal bullet margins updated to match this.
- Consistent margin for sub-lists.
- System back-end markdown renderer (For pages) updated with a custom
  list item renderer to apply class for to align with front-end renderer.
   - This means that task list items will be consistent with the preview
     and not render a number/bullet.
- Indentation styles for task list items fixed to be visually indented.

For #2854 and #2837