drivers: sensor: APDS9306: Add lux conversion

- Add lux conversion to APDS-9306 driver
- Change settings of gain, resolution and
frequency to index-based settings
- Add Device Tree overlay sample for APDS-9306
- Fix wrong board name in light_polling README
- Add value checks for the attribute set API call
- Remove the reading of the sensor attributes
from the sensor and use buffered values instead
- Rename `frequency` property to `measurement period`

Closes #91104

Signed-off-by: Daniel Kampert <DanielKampert@kampis-elektroecke.de>