Add datasets + samplers tutorial

[hfangcat]

Adding a new tutorial for datasets and samplers according to #2418.

Weird points here (to be fixed later):

1. The ChesapeakeCVPR download link is closed, I used my previous saved zip.
2. The ChesapeakeCVPR dataset is a bit large to download, which might not be suitable for a beginner tutorial, it would be good if we could provide a subset for the dataset (or use other alternative datasets).

[adamjstewart]

Can you remove the changes to pretrained/transforms from this PR?

[hfangcat]

Can you remove the changes to pretrained/transforms from this PR?

done!

[adamjstewart]

This tutorial doesn't really add anything that isn't already covered in the Introduction to TorchGeo tutorial. I would like to go much deeper, including the structure of GeoDataset R-trees, the class hierarchy (including RasterDataset and VectorDataset), how to use Raster/VectorDataset for generic uncurated data, the different splitters available, sampler ROIs, etc.

Also, the tests aren't passing. We can only use toy datasets in our tutorials due to time/space constraints.

[hfangcat]

This tutorial doesn't really add anything that isn't already covered in the Introduction to TorchGeo tutorial. I would like to go much deeper, including the structure of GeoDataset R-trees, the class hierarchy (including RasterDataset and VectorDataset), how to use Raster/VectorDataset for generic uncurated data, the different splitters available, sampler ROIs, etc.

Also, the tests aren't passing. We can only use toy datasets in our tutorials due to time/space constraints.

I agree with the deeper tutorial, but there is no time to do that for the AGU tutorial now. I fixed the ruff but the dataset (download issue) would be fixed later...

[adamjstewart]

Well, it can't be merged without passing tests. Also, it doesn't contain any new content that isn't shown in the introduction.