Refactor Queue as a Template

[AsimmHirani]

I think it would be a safer and more C++ style usage of the Queue's to take a template argument T and a runtime queue-size as the only constructor argument.

Something like:

struct MyEvent {
  uint32_t id;
  uint16_t element1;
  uint16_t element2;
};

...

cpp_freertos::Queue<MyEvent> event_queue(5); // Event queue that holds 5 MyEvents

The rationale here is the specialization makes the type that is inside the queue well known, and functions that return objects can now take T& instead of pointers, preventing null pointer errors at compile time.