Make AnalogIn.value return always 16 bit?

The CP standard for `AnalogIn.value` is 16 bit:
https://docs.circuitpython.org/en/latest/shared-bindings/analogio/index.html#analogio.AnalogIn.value

This library wants to follow same convention:
https://github.com/adafruit/Adafruit_CircuitPython_seesaw/blob/fd26309627c0758c982d272b6c708322102bddbf/adafruit_seesaw/analoginput.py#L34

[NeoSlider](https://www.adafruit.com/product/5295) (others?) return 10 bit:
```python
Adafruit CircuitPython 7.1.1 on 2022-01-14; Adafruit ItsyBitsy M4 Express with samd51g19
>>> import board
>>> from adafruit_seesaw.seesaw import Seesaw
>>> from adafruit_seesaw.analoginput import AnalogInput
>>> neoslider = Seesaw(board.I2C(), 0x30)
>>> potentiometer = AnalogInput(neoslider, 18)
>>> potentiometer.value
1023
>>> potentiometer.value
943
>>> potentiometer.value
451
>>> potentiometer.value
0
>>>
```

Start with the AnalogInput implementation in analoginput.py and compare its value behavior with the CircuitPython AnalogIn standard and the linked seesaw implementation. The work is done when AnalogIn.value consistently follows the 16-bit convention instead of returning the observed 10-bit range; no test file is mentioned.

Written by the indexing model from the issue text.