drivers: sensor: shell: make channel and attribute name tables as const

Make `sensor_channel_name` and `sensor_attribute_name arrays` to use
`const char *const`. This ensures full immutability of the tables,
placing them entirely in the `.rodata` section and reducing usage
of the `.data` segment.

Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>