seastar::logger is using the compile-time format checking by default if
compiled using {fmt} 8.0 and up. and it requires the format string to be
consteval string, otherwise we have to use `fmt::runtime()` explicitly.
so adapt the change, let's use the consteval string when formatting
logging messages.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#16612