Tests

CI: remove test/test_busy_worker.rb, clean up thread_pool.rb #8

Job	Run time
RuboCop linting	13s
skip_duplicate_runs / Skip Duplicate Runs	9s
ubuntu-22.04 jruby	3m 47s
ubuntu-22.04 jruby no SSL	3m 23s
ubuntu-22.04 jruby-head	3m 58s
ubuntu-20.04 2.4	4m 58s
ubuntu-20.04 truffleruby	3m 2s
ubuntu-20.04 2.5	3m 9s
ubuntu-20.04 truffleruby-head	3m 41s
ubuntu-20.04 2.6	2m 20s
ubuntu-22.04 truffleruby	2m 43s
ubuntu-20.04 2.7	2m 45s
ubuntu-22.04 truffleruby-head	3m 7s
macos-13 jruby	4m 9s
ubuntu-20.04 3.0	2m 12s
macos-14 jruby	3m 14s
ubuntu-20.04 3.1	3m 19s
macos-13 truffleruby	5m 45s
ubuntu-20.04 3.2	2m 17s
ubuntu-20.04 3.3	2m 39s
ubuntu-20.04 head	2m 33s
ubuntu-22.04 3.1	2m 26s
ubuntu-22.04 3.2	2m 16s
ubuntu-22.04 3.3	2m 46s
ubuntu-22.04 head	2m 42s
ubuntu-24.04 3.1	3m 0s
ubuntu-24.04 3.2	2m 32s
ubuntu-24.04 3.3	2m 50s
ubuntu-24.04 head	2m 22s
macos-13 2.4	6m 51s
macos-13 2.5	3m 26s
macos-13 2.6	3m 17s
macos-13 2.7	3m 36s
macos-13 3.0	3m 45s
macos-13 3.1	3m 4s
macos-13 3.2	3m 10s
macos-13 3.3	4m 26s
macos-13 head	3m 51s
macos-14 3.0	3m 23s
macos-14 3.1	2m 46s
macos-14 3.2	3m 12s
macos-14 3.3	3m 30s
macos-14 head	2m 57s
macos-15 3.1	3m 0s
macos-15 3.3	3m 47s
macos-15 head	3m 25s
windows-2022 2.4	5m 45s
windows-2022 2.5	5m 3s
windows-2022 2.6	4m 26s
windows-2022 2.7	4m 0s
windows-2022 3.0	2m 31s
windows-2022 3.1	3m 4s
windows-2022 3.2	2m 45s
windows-2022 3.3	3m 48s
windows-2022 ucrt	2m 9s
windows-2022 mswin	2m 34s
windows-2022 2.7 no SSL	3m 44s
ubuntu-20.04 2.7 no SSL	2m 12s
ubuntu-22.04 head yjit	2m 47s
ubuntu-22.04 2.4 rack2	4m 52s
ubuntu-22.04 3.2 rack2	5m 29s
ubuntu-22.04 2.4 rack1	4m 14s
	3h 25m 6s

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