Script for easy download of datasets and splits

[blazejba]

Problem:
Currently links to download the mixes and splits are hidden in the configuration files, e.g.:

graphium/expts/neurips2023_configs/base_config/large.yaml

Line 71 in 41a1172

# wget https://storage.googleapis.com/graphium-public/datasets/neurips_2023/Large-dataset/LINCS_L1000_VCAP_0-4.csv.gz

tdcommons.ai introduces more datasets for single prediction tasks, useful for the evaluation of pre-trained models:
https://tdcommons.ai/single_pred_tasks/

Solution:
Write a script that allows downloading selected or all datasets and splits easily.

Include:

• ToyMix,
• LargeMix,
• UltraLargeMix,
• TDC/single_prediction_tasks.