Run clang-format on the repo, add a github action to check formatting

[SLieve]

• Added a few clang-format directives to maintain ordering of includes:

  <angle-bracket includes> at the top
  
  <roaring/anything> below that
  
  "quoted includes" below that
  

• Formatted the repo with tools/clang-format.sh
• Marked the formatting commit as to-be-ignored by git blame, this should work with github too.
• Reordered some includes where there was still breakage, added comments to prevent futher reordering.
• Added a github action to check format against clang-format.
  • Note: This adds a github action dependency on https://github.com/DoozyX/clang-format-lint-action

[lemire]

Can you add instructions related to clang-cl under: .github/PULL_REQUEST_TEMPLATE.md and maybe somewhere as part of the README.md, or in an CONTRIBUTING.md file.

I don't object to your change, but I don't want to have to explain to people contributed code that they need to use clang-cl. This needs to be documented. Otherwise it creates a lot of bureaucratic exchanges.

Be mindful that not everyone uses clang-cl, so that's not entirely contributor friendly. (I personally do not object, to be clear.)

[SLieve]

Done. Note that the requirements are actually even a bit more strict: run a specific version of clang-format (currently stable version 17). This avoids inconsistent formatting. If you have any suggestion on making this smoother, I'm happy to take them onboard.

[lemire]

@Dr-Emann Can you review?

[Dr-Emann]

Might be worth a dockerfile with clang format installed, and a script that tries clang-format (checking the version), clang-format-17 and if neither work, using a docker container with the code mounted as a volume, to make it easier to format locally.

[lemire]

@Dr-Emann I coded something up with Docker: #580

Requiring users to have docker is a bit bad, but at least it will be consistent once they have it. Chasing the right clang-format version is terrible.

[SLieve]

Nice, yes using a bundled docker container sounds much nicer.

[lemire]

We should be able to merge this.

[Dr-Emann]

Personally prefer a longer line length, but happy to have automated formatting, like they say about gofmt:

Gofmt's style is no one's favorite, yet gofmt is everyone's favorite.