Reformat all code

It happens again and again that we have PRs with lots of reformatting and only some business logic change. Let's discuss in here how to format (I personally don't care as long as its clearly defined and consistent), and then do a reformat everything PR. Ideally, we find or pin whatever formatted the existing code, make sure that everyone has that congifured and keep it that way as it was "good" enough imo.

@xiangxn @AmmarYousefM @abitmore preferences?

Start by reviewing the repository's existing formatting setup and the reformatting problems described in recent pull requests. The issue does not name files, tests, or a formatter, so first establish the formatting standard and how it is configured. Done means an agreed, consistent format and a complete reformatting pull request.

Written by the indexing model from the issue text.