Optimize output vector adapter write (#3569)

* Add benchmark for cbor serialization and cbor binary data serialization

* Use std::vector::insert method instead of std::copy in output_vector_adapter::write_characters

This change increases a lot the performance when writing lots of binary data.

include/nlohmann/detail/output/output_adapters.hpp

@@ -53,7 +53,7 @@ class output_vector_adapter : public output_adapter_protocol<CharType>
     JSON_HEDLEY_NON_NULL(2)
     void write_characters(const CharType* s, std::size_t length) override
     {
-        std::copy(s, s + length, std::back_inserter(v));
+        v.insert(v.end(), s, s + length);
     }
 
   private: