Fix formatting issues with lists of elements

This fixes an issue with the formatting of lists of elements (for instance, the selected columns in a Select query).

To do so I have implemented a tokenize_list functions that acts similarly to more_itertools.intersperse but additionally accolates the separators to the element that precedes them. We could drop the more_itertools dependency by adding some sort of accolate flag to allow tokenize_list to emulate the behavior of intersperse. What's your opinion on this potential feature?