before this change, we rely on the default-generated fmt::formatter
created from operator<<, but fmt v10 dropped the default-generated
formatter.
in this change, we define formatters for `db::functions::function`.
please note, because we use `std::ostream` as the parameter of
the polymorphism implementation of `function::print()`.
without an intrusive change, we have to use `fmt::ostream_formatter`
or at least use similar technique to format the `function` instance
into an instance of `ostream` first. so instead of implementing
a "native" `fmt::formatter`, in this change, we just use
`fmt::ostream_formatter`.
Refs #13245
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#17832
8bab51733f