Draft: Add c8 air shower to CI

Since c8_air_shower was moved from examples to applications, it was no longer run on the CI. This adds it back into rotation and the python examples will be run on its output (except for the example with radio waveforms, which runs on the output from radio_em_shower).

The code approval procedure is described in the wiki: Code approval procedure wiki

• The MR is without WIP/Draft status
• Make sure the most recent CI jobs (config, quality, build_test_example) all run fine with no failures
  • if "check clang-format" failed: the code contributor has to run ./do-clang-format.py --apply eventually with the --all option
  • if "check copyright" failed the code contributor has to run./do-copyright.py --add=20xy
• Make sure also the jobs with MR-label ready for code review succeed. This includes the optional jobs, in particular 'coverage', 'release-clang-8", "release-u-18.04" and make sure no problems occur. You may have to trigger a pipeline manually to check this.
• Check in the "coverage" job output that the coverage did not decrease. It should always stay, or increase. If it decreased --> ask contributor to add further needed unit tests, and check coverage report.
• On the MR page, open the "Open in Web IDE" tool
  • Check if the provided solution solves the Issue, discuss on gitlab
  • Check that all changes are actually related to the issue
  • There are no debug statements left, not even commented out
  • Check all changes for coding rules and guidelines
• When all above is done:
  • Add MR label "Code Review Finished"