Don't leave Nanny stuck in closing status when worker kill times out (fix flaky test_chaos_rechunk)

[crusaderky]

test_chaos_rechunk frequently hangs, e.g. https://github.com/dask/distributed/actions/runs/28594679995/job/84786875121?pr=9315

This is due to an underlying race condition in Nanny which is triggered on very slow hosts (like Windows CI frequently is).

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

   19 files   -     21     19 suites   - 21   7h 8m 50s ⏱️ - 7h 6m 35s
  100 tests  -  4 055    100 ✅  -  3 870    0 💤  -   180  0 ❌  - 5 
1 900 runs   - 77 520  1 800 ✅  - 73 412  100 💤  - 4 103  0 ❌  - 5 

Results for commit b1bef38. ± Comparison against base commit 2d43f7f.

This pull request removes 4155 and adds 100 tests. Note that renamed tests count towards both.

distributed.cli.tests.test_dask_scheduler ‑ test_dashboard
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_allowlist
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_non_standard_ports
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_port_zero
distributed.cli.tests.test_dask_scheduler ‑ test_defaults
distributed.cli.tests.test_dask_scheduler ‑ test_hostport
distributed.cli.tests.test_dask_scheduler ‑ test_idle_timeout
distributed.cli.tests.test_dask_scheduler ‑ test_interface
distributed.cli.tests.test_dask_scheduler ‑ test_multiple_protocols
distributed.cli.tests.test_dask_scheduler ‑ test_multiple_workers
…

distributed.tests.test_stress ‑ test_chaos_rechunk[1-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[10-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[100-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[11-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[12-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[13-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[14-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[15-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[16-100]
distributed.tests.test_stress ‑ test_chaos_rechunk[17-100]
…

♻️ This comment has been updated with latest results.