Add updateMyDatasetId helper to useDatasetManager

### 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