OPIK-472 dataset items CRUD tests

[AndreiCautisanu]

Details

Added tests for CRUD operations for dataset items.
Test coverage:

1. Dataset item insertion - all possible combinations (insert items via the UI/SDK into dataset created via UI/SDK - check data correct and in sync between UI and SDK)
2. Dataset item modification - update dataset items with new data via the SDK and check the change is propagated and visible in both UI and SDK
3. Dataset item deletion - delete dataset item via both the SDK and the UI and check that the removal is propagated to both UI and SDK and that the new dataset is displayed/returned correctly (deleted item is no longer present)
4. Dataset item clearance - mass delete every item in the dataset by using dataset.clear() and check that the dataset appears as empty in both UI and SDK

7 test instances total. Tests 2, 3, and 4 are only done on datasets created via SDK and items inserted via the SDK to save on time (insertion and creation via all other ways already tested in test 1). @ferc let me know if you feel it's necessary to add the combinations from test 1 to the other tests, should be as simple as adding parametrization to all of them.

[AndreiCautisanu]

Ran sanity, datasets, and all_features successfully: https://github.com/comet-ml/opik/actions/workflows/end2end_suites.yml