Update dependencies and refactor RNG usage to StdRng

[ekkolon]

Closes #

📑 Description

This PR targets an update of rand to version 0.9.3 to get rid of a (low) CVE report for some rand versions. Additionally, this update also mandates an update of num-bigint-dig to the latest version.

Although rand v0.9.3 still exposes OsRng, we move away from it in this PR and use StdRng instead. We do this, in order to simplify future version updates of the rand abd num-bigint-dig crates. In particular, num-bigint-dig does not yet use the newly introduced RngExt trait by the rand crate, which blocks updating to rand 0.10.1 directly.

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information