Test and simplify more rust code snippets on the website

#4133 made it possible to hide lines in rust codeblocks. This opens up two opportunities ## Better Testing We should revisit all rust codeblocks with `ignore` and `no_run`, remove those annotations and fill in hidden missing context. So that the code snippets are gauranteed to be correct. ## Brevity We could revisit existing tested rust codeblocks and identify and hide contents irrelevant to the topic of the page/section. **Questionaire** _(Optional)_ - [ ] I'd like to write this documentation - [ ] I'd like to write this documentation but I'm not sure what's needed - [x] I don't have time to add this right now, but maybe later