chore: Let rustfmt format code in doc comments

[sbernauer]

Enable format_code_in_doc_comments and let cargo +nightly-2025-10-23 fmt --all format the code.

The unstable feature isn't perfect, but in my opinion this is a significant improvement.

[sbernauer]

Well we have a problem... rustfmt adds trailing whitespaces (which arguably isn't great).
As we have a trailing-whitespace pre-commit hook, there is no way to pass CI, as either trailing-whitespace or rustfmt will complain :D
I removed the problematic lines in 7cf2855, so the CI should hopefully turn green

[Techassi]

I removed the problematic lines in 7cf2855, so the CI should hopefully turn green

They were there on purpose. Too bad we have to remove them to avoid these weird spaces being inserted...

[sbernauer]

I looked through the diff again. Yes, the removed empty lines aren't great, but in my opinion the benefits of the formatted code snippets by far outweigh that.

[Techassi]

Yes, I agree. I just hope this feature improves in the future or there will be more granular control over this.

[sbernauer]

Merging to get this in (and potentially cut a release). #1130 will fix the pre-commit