[Meta] POC: introduce clang-format

[Razish]

DO NOT MERGE

This is a proof of concept for what introducing clang-format would look like.

Highly destructive for forks, but so much nicer to work with. I typically work with format-on-save, but have provided a helper script (scripts/format-code.sh) that could also be repurposed by CI to check if PRs adhere to code formatting rules.

Ref #1202