Fix: pengine: Don't use fprintf in formatted output.

Instead, use the formatted output functions like begin_list, list_item,
and pcmkindented_printf. This also allows condensing most of
pecommon_output_text and _html into a single function and then only
keeping the differences in those original functions. Lists are used
more thoroughly in all functions.

With that done, the pre_text and child_text variables can be removed.