Group doctests output

[jonatanklosko]

We should capture all outputs for each doctest and show together with the doctest. The question is how to show output for the successful doctests, for example we can make the groups collapsible.

[josevalim]

Here is a thread with inspirations about the UI: https://twitter.com/josevalim/status/1595535792814059520

Examples are: playwright, cypress, jasmine, etc.

[josevalim]

Something to consider is if failing tests should abort notebook execution, especially in shared apps.

[josevalim]

Closing in favor of #1936.