refactor people description messages

[minhnh]

Currently in the repository there's Person.msg and Face.msg. Person.msg do not use Face.msg.

There's also the provided people_msgs/Person from wg-perception (but ros-<version>-people-msgs can be installed independently). This message, however, do not have fields for point clouds, RGB, or key points (for pose detection).

We should discuss and decide on a unified message to represent people.

Potentially related to b-it-bots/mas_domestic_robotics#152.

[argenos]

I see two options:

• Use the people_msgs/Person in our message definition together with our additional fields
• what you proposed beforehand: Use a similar format

I'm partial to the second. @alex-mitrevski @PatrickNa thoughts?

[minhnh]

Another approach for people description messages from intel ROS 2 OpenVINO project may also give some inspiration.