ci: build and test the compiler with GCC 14

[zerbina]

Summary

Add a CI workflow for making sure the most recent version of common C compilers work. Only GCC 14 is tested at the moment.

Details

• the in-beta 24.04 Ubuntu runner image is used, since it comes with GCC 14 installed
• the compatibility job builds the compiler, tools, and tests with GCC 14
• two test cases that currently fail to compile (due to -Werror=incompatible-pointer-types) are split into standalone test files and marked as known issues
• the workflow is configured to run for push and PR events (except for in-draft PRs)

[zerbina]

/merge

[github-actions[bot]]

Merge requested by: @zerbina

Contents after the first section break of the PR description has been removed and preserved below:

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## To-Do * [x] ~mark the remaining failing tests as known issues~ * [x] write a proper commit message ## Notes for Reviewers * this should prevent further regressions from going by unnoticed