Refactor: libcrmcommon: pcmkoutput_t in pcmkxml_show in xml_display

And rename log_xml_changes_recursive() to show_xml_changes_recursive().

These are the minimum modifications required to enable functions within
xml_display.c to call pcmkxml_show() with a pcmkoutput_t argument.
For now, pcmkxml_log_changes() creates a new output object, passes it
to show_xml_changes_recursive(), and frees it before returning. Soon
pcmkxml_log_changes() will also accept a pcmk__output_t argument.

log_data_element() now also creates and frees a new output object. There
are no plans to change that further, since the function is public and
deprecated.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>