Fix the 4 ignored tests covering persisted durability fault coverage

**After #4132 is merged.**

Each test below carries its reason in the `#[ignore]` attribute and its doc comment.

| Test | Location |
|---|---|
| `given_a_completed_write_when_the_process_is_sigkilled_then_the_bytes_should_not_survive` | `core/integration/tests/cluster/crash_durability.rs:878` |
| `given_the_cluster_simulator_when_seeding_a_topic_then_a_persisted_policy_should_be_expressible` | `core/simulator/src/lib.rs:7723` |
| `given_a_retired_writer_when_reacquiring_then_the_drain_wait_should_be_executor_agnostic` | `core/simulator/src/storage/tests.rs:2741` |
| `deleting_and_recreating_a_partition_fences_an_old_writer_completion` | `core/simulator/src/storage/tests.rs:852` (pre-existing) |

```
cargo test -p simulator --lib -- --ignored
cargo test -p integration given_a_completed_write -- --ignored
```

Remove each `#[ignore]` once it passes.

After #4132 is merged, start with the four ignored tests and their #[ignore] reasons and doc comments: core/integration/tests/cluster/crash_durability.rs:878, core/simulator/src/lib.rs:7723, and core/simulator/src/storage/tests.rs:2741 and :852. Run the two cargo test commands in the issue, then address each test's stated failure. Done means all four tests pass and their #[ignore] attributes are removed.

Written by the indexing model from the issue text.