Add support for multiple csv segmented by var

[savente93]

Issue addressed

#453

Explanation

So I don't think this PR addresses an issue exactly, but it was something that I setup in #486 and wanted to finish anyway. I think it makes significant progress if not outright solve #453 (not totally sure which of the two it is, I'll leave that for the reviewer decide, or we can discuss it during stadnup/refinement) and makes some additional progress towards #372.

This simply adds the possibility for open_mfcsv to not only parse files per id, but also files per variables containing all ids (though not at the same time). The resulting dataset is the same as when the same data was segmented by id. I think it's a nice flexibility to have.

Checklist

• Updated tests or added new tests
• Branch is up to date with main
• Tests & pre-commit hooks pass
• Updated documentation if needed
• Updated changelog.rst if needed

Additional Notes (optional)

Add any additional notes or information that may be helpful.

[savente93]

Makrking this as ready for review as the failure in the CI seems to happen after all the tests have passed. Possibly it's somehthing with the report generation. I'm investigating that seperately.

[savente93]

For posterities sake, the CIs crach with the following message:

---------- coverage: platform linux, python 3.9.17-final-0 -----------
Coverage XML written to file coverage.xml

================= 143 passed, 65 warnings in 283.67s (0:04:43) =================
double free or corruption (!prev)
/home/runner/work/_temp/cb436074-82f6-48ae-bf0a-9afa0e4f349b.sh: line 1:  2714 Aborted                 (core dumped) python -m pytest --verbose --cov=hydromt --cov-report xml

[savente93]

note to self: add to doc index

[Tjalling-dejong]

LGTM 👍