This shouldn't impact any existing users, because it depends on an environment variable being set. This will enable us to rollout gradually when we're ready.  For now, there are still a few things to be done, primarily improving kagglesdk authorization.

http://b/379083750

Rough implementation using kagglesdk

The SQL statements don't contain an `ORDER BY` clause, so the ordering
can't be an intentional check for this exercise. This exercise happens
to work most of the time because BigQuery tends to return results in the
same order, but sometimes it doesn't. Learn users shouldn't have to deal
with this non-determinism in the check.

http://b/415948668

Sort the results before comparison

This environment variable was added in kaggleazure PR 36128. It is set on all Learn sessions. It refers to the version of the exercise the user forked from.

Note that this is all still behind a feature flag, so this code is a no-op for now.

http://b/379083750

Use the `KAGGLE_LEARN_SESSION_ID`

Enables Kaggle Notebooks to continue to show nudges even if using kagglesdk under the hood.

http://b/379083750

Post response back to the outer iframe.

In testing, I was assuming this would already be an int, but it looks like KKB puts all environment variables as strings.

http://b/379083750

Cast KAGGLE_LEARN_SESSION_ID to int