Add DecathlonDatalist to enhance decathlon style loading

[Nic-Ma]

Is your feature request related to a problem? Please describe.
Currently, we already have several useful utilities to load or sample the decathlon datalist, would be nice to add a class to combine and enhance the feature.
We already have a reference implementation in NVIDIA Clara and can config it in the JSON file:

{"datalist": {"name": "DecathlonDatalist", "args": {XXX}}},
{"dataset": {"name": "CacheDataset", "args": {"data": "@datalist"}}}

I will try to reimplement it according to MONAI style.

[wyli]

Hi Nic, would be great to have more details on this, is it an enhancement of

MONAI/monai/apps/datasets.py

Line 152 in 0935d5a

class DecathlonDataset(Randomizable, CacheDataset):

[Nic-Ma]

Hi @wyli ,

DecathlonDatalist is mainly supposed to load "decathlon style" datalist from JSON file, and do more logic.
It's a class level combination of the utilities in this file:
https://github.com/Project-MONAI/MONAI/blob/dev/monai/data/decathlon_datalist.py

Thanks.