Various to-dos

[dpshepherd]

For @dpshepherd (reminding myself):

1. Update RLGC to match changes in merfish3d-analysis
2. Clean up registration and fusion so that the API is clear
3. Improve downsampling for multiscale ome-ngff (currently striding for fast generation)
4. Test registration and fusion with non-OPM data
5. Make clear what metadata we need for registration and fusion
6. Compare our registration/fusion with most recent updates to multivew-stitcher

[dpshepherd]

After conversation with Hongquan, ensure that TileFusion:

1. works with or without GPU
2. works on 2D data

[dpshepherd]

See #15 for efforts on the tile fusion to-dos.