ak4619/cal: test sample widths other than W=16

[schnommus]

Initially raised in https://github.com/apfelaudio/eurorack-pmod/discussions/37

There's nothing limiting us to W=16-bit samples (maximum from AK4619 is 32 bits per sample).

We should try some different sample widths and make sure the rest of the modules (calibrator, demos) all still work.

The calibrator module cal.sv would need to be modified to be parameterized across different fixed-point representations.