test: Add unique offsets to ids generated by TestContext to increase test correctness

[Simon-Laux]

and fix the mistakes in tests that get discovered by this.

• add tests for setting the offset
• fix the tests that were discovered by this
• find a solution for the golden test problem (golden tests expect the offset to be deterministic, currently it is derived from the account id which is random)

closes #6799

[Simon-Laux]

Seems my approach of just dividing the random number does not work, this approach is not compatible with the golden tests:

    thread 'tests::verified_chats::test_verified_chat_editor_reordering' panicked at src/test_utils.rs:977:13:
    assertion failed: `(left == right)`: To update the expected value, run `UPDATE_GOLDEN_TESTS=1 cargo test`

    Diff < left / right > :
    <Group#Chat#1979039380: Group [3 member(s)] 🛡️
    >Group#Chat#11: Group [3 member(s)] 🛡️

we could add an id to the named accounts, as this offset needs to be unique account per per test, but not unique across all tests.

[Hocuri]

UPDATE_GOLDEN_TESTS=1 cargo nextest run