feat: support Encord datasets

[eloy-encord]

Add support for Encord datasets.

Still a WIP because while the dataset class returns what should be the expected data for the data loader is probably not in the right format (which need testing and posterior fix).

All feedback is welcomed 😊! This PR is going to be in draft until the tests are ✅ .

[Jim-Encord]

Bugs:
I've tried using two different datasets in Encord rather than rsicd so as to use something smaller.
If I use the crab or accordion dataset (which we all have access too), I get:

File "/Users/encord/Documents/cord/text-to-image-eval/.venv/lib/python3.11/site-packages/encord/http/bundle.py", line 179, in bundled_operation
    assert len(result) == 1, "Expected a singular response for a singular request!"

whilst downloading the dataset from Encord.
I can make a PR including this dataset, so we can test on that.

[eloy-encord]

@Jim-Encord I'm not sure where that error came from but the dataset output wasn't compatible with the model's input. Now with my latest fix it should run. At least I have run one complete dataset and it's ok. Still downloading the example one (rsicd) and will leave it running all night as it's super slow in the local.

[Jim-Encord]

LGTM. Have tested it with one other Classification dataset but probably want Frederik to look at it also