Refactor: libcrmcommon,libpacemaker,tools: convert pcmk__output_new() to standard return codes

Coincidentally, after submitting 55ebd89, we did get our first report of
conflicting values in the wild (clbz#5419). One of the conflicting values,
pcmk_err_unknown_format, was only used by the internal function
pcmk__output_new(). Convert it to use the new standard codes.

While this doesn't fix the incompatibility with glibc on HP PA-RISC, it does
reduce any potential impact of renumbering the old codes on that platform.