Refactor: libcrmcommon: New pcmk__xml_fmt_options enum

Intended to replace public xml_log_options enum.

xml_log_option_text is used only in internally dead code; we need to
keep it only in case an external caller passes it to log_data_element().

We don't need equivalents for xml_log_option_dirty_add or
xml_log_option_diff_all. Those will be addressed in later commits.

This goes in xml_internal.h instead of logging_internal.h because it's
not used exclusively in logging functions. The XML dump functions also
use it.

The next few commits aren't quite atomic in edge cases where external
callers call log_data_element() with unexpected options. However,
they're separated for ease of review. The commit to deprecate
xml_log_options will fix log_data_element().

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