Extract tests related to event-logging into separate file

[hendrikmakait]

Precursor to #8731

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

[github-actions]

Unit Test Results

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

    29 files  ±0      29 suites  ±0   11h 31m 0s ⏱️ - 1m 28s
 4 064 tests ±0   3 961 ✅ +4     97 💤 ±0  6 ❌  - 4 
55 981 runs  ±0  53 811 ✅ +6  2 163 💤 ±0  7 ❌  - 6 

For more details on these failures, see this check.

Results for commit 9b14d5a. ± Comparison against base commit 97dbdaa.

This pull request removes 12 and adds 12 tests. Note that renamed tests count towards both.

distributed.tests.test_client ‑ test_events_all_servers_use_same_channel
distributed.tests.test_client ‑ test_events_subscribe_topic
distributed.tests.test_client ‑ test_events_subscribe_topic_cancelled
distributed.tests.test_client ‑ test_events_unsubscribe_raises_if_unknown
distributed.tests.test_client ‑ test_log_event
distributed.tests.test_client ‑ test_log_event_msgpack
distributed.tests.test_client ‑ test_log_event_multiple_clients
distributed.tests.test_client ‑ test_log_event_warn
distributed.tests.test_client ‑ test_log_event_warn_dask_warns
distributed.tests.test_nanny ‑ test_log_event
…

distributed.tests.test_client ‑ test_warn_manual
distributed.tests.test_client ‑ test_warn_remote
distributed.tests.test_event_logging ‑ test_configurable_events_log_length
distributed.tests.test_event_logging ‑ test_events_all_servers_use_same_channel
distributed.tests.test_event_logging ‑ test_events_subscribe_topic
distributed.tests.test_event_logging ‑ test_events_subscribe_topic_cancelled
distributed.tests.test_event_logging ‑ test_events_unsubscribe_raises_if_unknown
distributed.tests.test_event_logging ‑ test_log_event
distributed.tests.test_event_logging ‑ test_log_event_msgpack
distributed.tests.test_event_logging ‑ test_log_event_multiple_clients
…

[phofl]

lgtm