Support for choosing what scale to segment in an OME-Zarr and checkbox to (de)select local Zarr storage

[krentzd]

Added support for choosing what scale to select when segmenting a multiscale OME-Zarr image:

1. SpinBox multiscale_level to select scale is revealed if image_layer is a multiscale OME-Zarr
2. Maximum value of multiscale_level is set according to the number of available scales
3. Resulting labels layer is scaled to correctly overlay to the full OME-Zarr image

Added checkbox to (de)select local Zarr storage:

1. FileDialog store_dir and LineEdit chunk_size is revealed when use_store_dir=True
2. When use_store_dir=False, no local Zarr storage is used