Add end-to-end tests at the end of Datalab quickstart tutorial

[jwmueller]

This tutorial has no tests for some reason: https://raw.githubusercontent.com/cleanlab/cleanlab/master/docs/source/tutorials/datalab/datalab_quickstart.ipynb

If you look at at the raw version of most of our other tutorials, eg:
https://raw.githubusercontent.com/cleanlab/cleanlab/master/docs/source/tutorials/image.ipynb

You'll notice they have a final hidden cell that is full of assert statements:

This hidden cell is essentially an end-to-end test of the code.

Goal: add a similar hidden cell to the Datalab quickstart tutorial.
The hidden cell should have asserts which check that:

1. the jaccard similarity between data detected as is_label_issue = True and actual known mislabels in the dataset is > 0.9 (or sufficiently high threshold)

2. that roc_auroc_score(label_quality_scores, Z) > 0.9 (or sufficiently high threshold), where Z ground-truth array with value 1 if this data point is correctly labeled, value 0 if it is truly a mislabel. This assert checks that the label quality scores appropriately rank the data.

3. the jaccard similarity between data detected as is_XYZ_issue = True and actual known instances of issue XYZ in the dataset is > 0.9 (or sufficiently high threshold).

Here XYZ = outlier, near duplicate, etc.

4. no other issue types beyond those expected were detected in this tutorial. Make sure this assert is forwards compatible. That is, if we add 3 new issue types to Datalab-defaults in the future, this same assert should be able to catch if any of these newly added issue types is suddenly detected in this tutorial.