Refactor: libcrmcommon: Remove internal use of xml_log_option_dirty_add

Except in already-deprecated log_data_element(), since it affects
behavior there. We won't be replacing this option with an internal
pcmk__xml_fmt_dirty_add.

Also add a compat note to log_xml_changes_recursive(). Currently it's
only called with one specific value (pcmk__xml_fmt_pretty) for the
options argument, so we won't need that argument after
log_data_element() is removed. We need it now only because an external
caller could call log_data_element() without the pretty/formatted
option.

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