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>
34cab80103