C++: mini_reflect: Add DefaultTypeTable (#4614)

* mini_reflect: Add DefaultTypeTable

Currently it's very easy to make a mistake when it comes to
instantiating the TypeTable to print a buffer because it is not type
safe.

This will allow us to write safer cpp code:

flatbuffers::FlatBufferToString(reinterpret_cast<const uint8_t *>(&t),
                                decltype(t)::DefaultTypeTable());

* c++: mini_reflect: update generated code

* Ensure types and names are set for mini_reflect

* c++: mini_refelct: update unit tests with new typed TypeTable

* Adding PR feedback of sylte and naming convention