Check that the code gallery programs compile and run.

[bangerth]

Do this for every release, just before we make the release, then move the release milestone to the following release.

[marcfehling]

We can also set up the CI to do it, similar to the preCICE one we have running now.

For this we can use the deal.II docker images, and set up a cronjob that executes the workflow, let's say, every sunday.

We basically already have a working gihub-actions script in dealii/code-gallery#93. We need to enhance it to span all tutorial programs.

EDIT: We can set up the scheduled jobs that they create issues automatically upon failure. That is a really neat feature :)

[bangerth]

I'd be in favor of this, though in the end it still boils down to someone having to look at the results and, if necessary, do something about it.

[tamiko]

We can also make compiling the code gallery part of the regression testsuite. This would require no infrastructure changes.

[marcfehling]

dealii/code-gallery#133 will also help setting up CI and regression testers.

[bangerth]

I can compile the current set of programs, and could run them a month or so ago. Bumping to the next release.

[bangerth]

We aren't done with this, but there are now 16 of these tests already in tests/examples, with #16988 and #16989 currently pending. This is decent progress.