Napari GUI: Parameter/config checking happens at widget runtime

[qin-yu]

Input should be checked and stopped at Napari interface before widget buttons get clicked.

[qin-yu]

What I meant was that widgets fails to run because input could be invalid. Now I want to make the checking while user is inputting.

[qin-yu]

This Issue refers to the parameters/configs put into the Napari GUI.

Actually some inputs are checked like

https://github.com/hci-unihd/plant-seg/blob/7acc49c0d5ecc0414898f11e179b83fc3a6367b2/plantseg/viewer/widget/io.py#L194

I also added some:

https://github.com/hci-unihd/plant-seg/blob/7acc49c0d5ecc0414898f11e179b83fc3a6367b2/plantseg/viewer/widget/predictions.py#L205

But configs/args put into functions still need to be checked by Pydantic.