before this change, we only consider "named_value<type>" as the declaration of option, and the "Type" field of the corresponding option is displayed if its declaration is found. otherwise, "Type" field is not rendered. but some logging related options are declared using `log_legacy_value`, so they are missing. after this change, they are displayed as well. Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>