Use test-unit-ruby-core gem #141

Job	Run time
ruby-versions / Generate Ruby versions	3s
ubuntu-20.04 2.3	39s
ubuntu-20.04 2.4	44s
ubuntu-20.04 2.5	1m 29s
ubuntu-20.04 2.6	1m 35s
ubuntu-20.04 2.7	1m 36s
ubuntu-20.04 3.0	32s
ubuntu-20.04 3.1	33s
ubuntu-20.04 3.2	27s
ubuntu-20.04 head	28s
ubuntu-20.04 jruby	1m 43s
ubuntu-20.04 jruby-head	1m 52s
ubuntu-20.04 truffleruby	1m 3s
ubuntu-20.04 truffleruby-head	1m 11s
ubuntu-22.04 2.3	36s
ubuntu-22.04 2.4	31s
ubuntu-22.04 2.5	1m 26s
ubuntu-22.04 2.6	1m 28s
ubuntu-22.04 2.7	1m 27s
ubuntu-22.04 3.0	26s
ubuntu-22.04 3.1	55s
ubuntu-22.04 3.2	25s
ubuntu-22.04 head	38s
ubuntu-22.04 jruby	1m 52s
ubuntu-22.04 jruby-head	1m 24s
ubuntu-22.04 truffleruby	1m 12s
ubuntu-22.04 truffleruby-head	1m 26s
macos-11 2.3	1m 16s
macos-11 2.4	54s
macos-11 2.5	2m 7s
macos-11 2.6	2m 9s
macos-11 2.7	2m 19s
macos-11 3.0	42s
macos-11 3.1	41s
macos-11 3.2	40s
macos-11 head	43s
macos-11 jruby	1m 32s
macos-11 jruby-head	1m 36s
macos-11 truffleruby	1m 36s
macos-11 truffleruby-head	2m 57s
macos-12 2.3	1m 7s
macos-12 2.4	1m 0s
macos-12 2.5	2m 34s
macos-12 2.6	2m 24s
macos-12 2.7	2m 12s
macos-12 3.0	39s
macos-12 3.1	49s
macos-12 3.2	55s
macos-12 head	58s
macos-12 jruby	1m 46s
macos-12 jruby-head	2m 11s
macos-12 truffleruby	2m 24s
macos-12 truffleruby-head	2m 34s
windows-latest 2.3	1m 21s
windows-latest 2.4	1m 45s
windows-latest 2.5	4m 50s
windows-latest 2.6	3m 22s
windows-latest 2.7	4m 12s
windows-latest 3.0	1m 24s
windows-latest 3.1	1m 30s
windows-latest 3.2	2m 4s
windows-latest head	3m 43s
ubuntu-latest jruby-9.1	1m 0s
ubuntu-latest jruby-9.2	2m 29s
ubuntu-latest jruby-9.3	1m 31s
	1h 37m 37s

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