CI: update the Rust version to the latest stable

[dannywillems]

The current version in the CI is 1.84. We should bump up the Rust version to the latest stable release.
We suggest to have a fixed version (like 1.90) and the latest stable to the CI.
There are also a few dependencies like proof-systems that should be using the latest stable too.

As part of this task, it would be nice to list all the dependencies that the Rust node and that we control - including the indirect dependencies (for instance, proof-systems uses ocaml-gen), and update the CI to test with the same Rust versions.

As part of this task, we also want to have the process documented on the website in the developers section.