Allow setting layer resolution for ipyvolume viewer

[Carifio24]

Currently only a single resolution is used for the entire viewer. This makes sense for the vispy viewer, which only has a single viewer-wide resolution, but the ipyvolume viewer allows setting max_resolution for each layer. We should update the exporter to allow setting the resolution layer-by-layer. Currently we take the maximum of the resolutions of all of the exported layers.