two-fer: add generator and regenerate tests

[ErikSchierboom]

Should be merged after #728 is merged

[github-actions]

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

If this PR does not affect the result of the test (or, for example, adds an edge case that is not worth rerunning all tests for), please add the following to the merge-commit message which will stops student's tests from re-running. Please copy-paste to avoid typos.

[no important files changed]

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[tasxatzial]

There's also an extra line at the end of the template and a generators/.problem-specifications directory

[ErikSchierboom]

There's also an extra line at the end of the template

That's actually intentional. See https://unix.stackexchange.com/questions/18743/whats-the-point-in-adding-a-new-line-to-the-end-of-a-file for the reasoning. TL;DR: it helps with merges and diffs

[ErikSchierboom]

@tasxatzial Updated!