Introduce CSV/TSV header row

[RobinTF]

As discussed with @joka921 the current CSV/TSV export doesn't properly print the headers as specified in the standard.
This PR fixes this issue and does some small-scale refactoring to reduce duplicated code

[joka921]

Thank you very much.

There are some small comments.
I am still trying to figure out whether we should leave this waiting for a little bit
(It does not hurt) and try to merge #546 first.

[RobinTF]

There are some small comments. I am still trying to figure out whether we should leave this waiting for a little bit (It does not hurt) and try to merge #546 first.

I think this decision should entirely depend on the state of #546
If it is close to being merged (matter of one or two days), then waiting might be a good option. However if there's still some development going on (say some refactorings of the class structure), then merging this PR first is the better option in my opinion because the structure needs to change with the arising merge conflicts anyways

[joka921]

I only want two more comments, which concern already existing code and one variable renaming
(the std::views::iota is not required:))

Thank you very much