This change splits out the formatting of simple single-line lists. A list
is considered "simple" if all of its elements are on one line, all
elements are literals (except heredoc) and there are no line comments.
As an exception, a heredoc string is allowed when it is the only element
in the list.
This fixes an issue with a single-line list with one element and a line
comment. The formatter used to pull the closing bracket on the same line
(after the comment), causing parse errors.
b07f6fa7a2