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 maybe some 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
• I don't have time to add this right now, but maybe later