Refactor: libcrmcommon: Add COMPAT to internally dead code text option

Commit ab0ef95 replaced all of this code with libxml serialization using
pcmk__xml_fmt_full (at the time called xml_log_option_full_fledged).

We unfortunately have to keep dump_xml_text() for now, because an
external caller could pass xml_log_option_text to log_data_element().

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