Add updateMyDatasetId helper to useDatasetManager

[nozomione]

Context

Epic: #391

Feature branch: feature/epic-refacter-use-dataset-manager-hook

In #393, we introduced a wrapper helper method updateMyDataset for the context state's setter setMyDataset.

We also have the context state myDatasetId and its setter setMyDatasetId which store and update the user-saved My Dataset ID.

To align with this new pattern, we want to create a wrapper helper method responsible for setting myDatasetId, which will also be called from the hook methods (e.g., createDataset) on API requests.

Problem or idea

We should replace all setMyDatasetId calls within the hook with the new wrapper method described above.

Solution or next step

1. Add a new method updateMyDatasetId that accepts the dataset ID fetched from the API
2. Replace the setMyDatasetId calls with this newly added wrapper method