Update material to Rust Edition 2024

[squell]

What is the scope of your suggestion?
A new Rust Edition will be coming out next month, and it has some changes (e.g. TIL that 'object safety' is now called 'dyn compatibility').

Describe what should be added/changed

• We should go through the modules and update references to old concepts and replace them with the new concepts
• We should go through the exercises and see if there's any place where the compiler (version 1.85) will complain about "this is old Rust edition stuff".

Describe a potential alternatives you've considered

• A dedicated section on "old Rust editions" would be nice to have to teach-rs. E.g. "what does it mean if i see extern crate somewhere?", although I think that sort of stuff should not necessarily be taught to new programmers.