Get field names and types of Message

[xander-m2k]

Feature Request

Feature description

Currently there is no possibility of getting message field info in rclcpp. In python libraryrosidl_python the function get_fields_and_field_types() exists, and does exactly what I want in rclcpp. Please implement this, this will make automation and conversion to other protocols much easier.

[hidmic]

This should be straightforward to implement. @xander-m2k contributions are most welcome.