Refactor P2P rechunk validation

[hendrikmakait]

Sibling to dask/dask#10336

• Tests added / passed
• Passes pre-commit run --all-files

[hendrikmakait]

cc @wence-

[github-actions]

Unit Test Results

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

       20 files  ±  0         20 suites  ±0   11h 28m 30s ⏱️ + 6m 14s
  3 679 tests +  3    3 569 ✔️ +  2     108 💤 ±0  2 ❌ +1 
35 580 runs  +32  33 813 ✔️ +30  1 765 💤 +1  2 ❌ +1 

For more details on these failures, see this check.

Results for commit 217bc3b. ± Comparison against base commit fdeb6b3.

This pull request removes 2 and adds 5 tests. Note that renamed tests count towards both.

distributed.dashboard.tests.test_scheduler_bokeh ‑ test_FinePerformanceMetrics_simulated_spill_no_crash
distributed.tests.test_scheduler ‑ test_cumulative_worker_metrics

distributed.tests.test_spans ‑ test_worker_metrics
distributed.tests.test_worker_metrics ‑ test_no_spans_extension
distributed.tests.test_worker_metrics ‑ test_reschedule
distributed.tests.test_worker_metrics ‑ test_send_metrics_to_scheduler
distributed.tests.test_worker_metrics ‑ test_user_metrics_weird

♻️ This comment has been updated with latest results.

[wence-]

OK, so now that dask does this validation, there is no need to repeat it here.