Those are all consumed by our parser, so they all support comments.
I was considering whether they should have a license header at all,
but in the end I decided to add it because those files are often created
by copying parts of real unit files. And if the real ones have a license,
then those might as well. It's easier to add it than to make an exception.
Note that run_test() calls coredumpctl in a loop because in certain
environments (1 vCPU unaccelerated QEMU VM) it might take quite a
while to process the coredump.