More flexible dataset class, or overide to allow multiple geometries

[bw4sz]

As DeepForest moves to 2.0 and support for boxes/polygons/points, we need to wary of places that are hardcoded for just boxes. One spot is in the dataset.TreeDataset class, which assumes boxes and even names the target key {"boxes":}

It connects here:

DeepForest/src/deepforest/main.py

Line 277 in fdfd55f

ds = dataset.TreeDataset(csv_file=csv_file,

Option 1. A master dataset class that works by detecting the geometry.

Option 2. Allow users to pass a dataset class

[bw4sz]

Related to #833