Update code style to use rust fmt.

[MichaelMauderer]

Pull Request Description

Updates the codebase/CI to use rust fmt style and updates the style guide.

[ci no changelog needed]

Important Notes

Check the different commits for better overview of the changes.

Checklist

Please include the following checklist in your PR:

• [ ] ~The CHANGELOG.md was updated with the changes introduced in this PR.~
• [ ] ~The documentation has been updated if necessary.~
• [ ] All code conforms to the Rust style guide.
• [ ] ~All code has automatic tests where possible.~
• [ ] ~All code has been profiled where possible.~
• [ ] ~All code has been manually tested in the IDE.~
• [ ] ~All code has been manually tested in the "debug/interface" scene.~
• [ ] ~All code has been manually tested by the PR owner against our test scenarios.~
• [ ] ~All code has been manually tested by at least one reviewer against our test scenarios.~