sensors: add new channel `SENSOR_CHAN_POS_DXYZ`

Add new channel: `SENSOR_CHAN_POS_DXYZ`, so that it is
consistent with other 3-axis channels.

Updated pytest, `sensor_shell` & `fake_sensor` accordingly.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>
6 files changed