Make ros_type_name and gz_type_name optional in ros_gz_bridge

[azeey]

Desired behavior

Since the ROS and Gazebo topic names are provided to ros_gz_bridge, it seems possible to determine the topic type names automatically. If there is a one-to-many or many-to-many mapping, we can either bail or provide sane defaults.

Alternatives considered

n/a

Implementation suggestion

n/a

Additional context

n/a