Rust: Default to 1.78 and update `rust_deps`

Alpine 3.20 is packaging Rust 1.78. Prior to having rustup available in the CI, we were using the same Rust version as Alpine. Considering Rust 1.74 is almost one year old (November 2023), it looks like a good idea to upgrade.

Besides, we run cargo update in src/rust_deps which notably means we start using ocaml-rs 1.0.1 (instead of relying on the beta). This version seems to support OCaml 5, which was not the case of the beta as far as I can tell.

Note that:

• Having ocaml-rs 1.0.1 seems to be a requirement for !15017 (merged) (to be confirmed, but this change remains valid in and on itself imo)

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR