Integrate checkpatch and llvm code formatter

[gparmer]

We should really not be reviewing style as much as we do. Integrate checkpatch¹² to offload some of it, and our auto-formatter ³ for the rest. Identify what style issues these do not cover, and seek out options.

Footnotes

1. https://docs.kernel.org/dev-tools/checkpatch.html ↩

2. https://unikraft.org/docs/contributing/testing/#using-checkpatchpl ↩

3. https://github.com/gwsystems/composite/blob/main/.clang-format ↩