This device was tested on a D455 but should work on any other RealSense camera
that supports camera and IMU streams (even the T265), given that you properly
configure the external SLAM config file.
This commit introduces the term `ddev` for a "Device-SLAM tracked device",
it will be useful to differentiate itself from the `hdev`
("Host-SLAM tracked device") that will be introduced in next commits.
Note that "config_realsense" json field was renamed to "config_realsense_device"
and the device's serial (used for tracking overrides) changed from
"Intel RealSense 6-DOF" to "Intel RealSense Device-SLAM".