[Bug]: Non-deterministic data generation in tests

[netrome]

Context

In signer/storage/model.rs we sometimes use the #[dummy(expr = "fake::vec![u8; 32]") annotation to generate block hashes and other byte arrays represented as vectors. However, this yields non-deterministic results even when using a seeded random number generator.

Definition of done

Generating faked model entities with a seeded random number generator should yield deterministic results.

[djordon]

This was mostly done in #1578 but there are several tests that need to be updated.