Ran rustfmt and added formatting checks to CI

[Kixiron]

• Ran rustfmt across the codebase
• Added rustfmt checks to the github ci

[Kixiron]

r? @HeroicKatora

[kornelski]

I think rustfmt checks in CI are counter-productive. It slows down CI feedback, and rejects PRs for trivial reasons.

But the worst effect of rustfmt is blowing up small code changes into big reformatting of entire blocks. It makes reviewing of PRs more difficult. Addition or deletion of a single line or word has a nice readable diff, but if it happens to push the code over some threshold in rustfmt, it can cause entire block to be rewrapped, and then it's harder to see what has actually changed.