Bump Rust + RefinedRust versions

[lgaeher]

Description of the changes

This updates the Rust version to 1.91-nightly, adapting the code accordingly in some places.
In a future MR, we should also adapt to edition = 2024. (I could take care of that)

Accordingly, this updates RefinedRust to the current version, adapting the annotated specifications to RefinedRust's new more compact specification format.

Type of change

• [ x ] Refactorization (non-breaking change which improves code quality)

How to test this PR?

CI should test that this does not break the build and verification.

[wojciechozga]

Hi Lennard, thanks for this MR, I see you did a lot of solid work. Could you also update the README inside the verification/ directory so that we have a human readable up-to-date overview of what has been verified so far? I refer to this https://github.com/IBM/ACE-RISCV/tree/main/verification

The extra poofs I refer are for example in below files:

• verification/rust_proofs/ace/proofs/proof_core_page_allocator_page_Page_core_page_allocator_page_UnAllocated_init.v
• verification/theories/page_allocator/page.v
• verification/theories/page_table/page_table.v

[lgaeher]

Thanks for the comments! I took a look over the readme and updated it where necessary.

This PR doesn't substantially change the amount of code that has been verified so far (this will be part of the future MR upstreaming new verification results). The new verification only includes some minor things, like strengthening the specs of read and write.
The extra proof files you're referring to should be covered by the current status for the page token, page allocator, and page table.

In the next MR, I'll also adapt the table to reflect the then-current status.

[wojciechozga]

Thank you! LGTM