Add debug checks for containers unexpectedly returning unknown values by copybara-service[bot] · Pull Request #1462 · google/cel-cpp

@jcking @copybara-github

Returning unknowns directly from containers (list, map, struct, and optional) is not and has not been supported. In fact there are known areas where it is possible for unknowns to be silently ignored if they were returned. As such, adding debug checks to prevent accidental reliance.

PiperOrigin-RevId: 751529259