thrift: add formatter for cassandra::ConsistencyLevel::type

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
cassandra::ConsistencyLevel::type.
please note, the operator<< for `cassandra::ConsistencyLevel::type`
is generated using `thrift` command line tool, which does not emit
specialization for fmt::formatter yet, so we need to use
`fmt::ostream_formatter` to implement the formatter for this type.

Refs #13245

Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>

Closes scylladb/scylladb#17013

thrift/handler.cc

@@ -48,6 +48,8 @@
 #include "db/config.hh"
 #include "locator/abstract_replication_strategy.hh"
 
+#include <fmt/ostream.h>
+
 #ifdef THRIFT_USES_BOOST
 namespace thrift_fn = tcxx;
 #else
@@ -63,6 +65,8 @@ using namespace  ::cassandra;
 
 using namespace thrift;
 
+template <> struct fmt::formatter<cassandra::ConsistencyLevel::type> : fmt::ostream_formatter {};
+
 class unimplemented_exception : public std::exception {
 public:
     virtual const char* what() const throw () override { return "sorry, not implemented"; }