Run clang-format on entire codebase

[alanking]

We should do this as part of the next "major" release.

If you're concerned about git-blame, the Black python formatter documentation introduced me to the nice concept of ignoring commits: https://git-scm.com/docs/git-blame#Documentation/git-blame.txt---ignore-revltrevgt

And there's even support in GitHub: https://docs.github.com/en/repositories/working-with-files/using-files/viewing-and-understanding-files#ignore-commits-in-the-blame-view

And here's the original documentation through which I discovered these things: https://black.readthedocs.io/en/stable/guides/introducing_black_to_your_project.html

Until then, we should update the .clang-format file to not use tabs so that we can actually use it.

[korydraughn]

Yes please do.