Resolves 4615
Previously only Vertical and Mixed enum variants of DefinitiveListTactic
were considered when rewriting pre-comments for inner items in
lists::write_list.
Because we failed to considering the SpecialMacro variant we ended up in
a scenario where a ListItem with a pre_comment and a pre_comment_style
of ListItemCommentStyle::DifferentLine was written on the same line as the
list item itself.
Now we apply the same pre-comment formatting to SpecialMacro, Vertical,
and Mixed variants of DefinitiveListTactic.
