Remove usage of IO internals. #702

Job	Run time
openssl-1.0.2u	3m 6s
openssl-1.1.0l	2m 39s
openssl-1.1.1t	2m 22s
openssl-3.0.8	4m 32s
libressl-3.1.5	2m 58s
libressl-3.2.7	3m 8s
libressl-3.3.6	3m 38s
libressl-3.4.3	3m 19s
libressl-3.5.3	3m 45s
libressl-3.6.1	3m 11s
libressl-3.7.0	3m 44s
openssl-3.0.8 fips	4m 10s
ruby-versions / Generate Ruby versions	3s
ubuntu-22.04 2.6	1m 27s
ubuntu-22.04 2.7	1m 8s
ubuntu-22.04 3.0	1m 14s
ubuntu-22.04 3.1	1m 29s
ubuntu-22.04 3.2	1m 24s
ubuntu-22.04 head	1m 15s
ubuntu-22.04 truffleruby	53s
ubuntu-22.04 truffleruby-head	59s
ubuntu-20.04 2.6	1m 25s
ubuntu-20.04 2.7	1m 15s
ubuntu-20.04 3.0	1m 25s
ubuntu-20.04 3.1	1m 10s
ubuntu-20.04 3.2	1m 7s
ubuntu-20.04 head	1m 7s
ubuntu-20.04 truffleruby-head	1m 10s
macos-latest 2.6	2m 2s
macos-latest 2.7	1m 44s
macos-latest 3.0	1m 43s
macos-latest 3.1	1m 27s
macos-latest 3.2	2m 18s
macos-latest head	1m 22s
macos-latest truffleruby-head	4m 9s
windows-latest 2.6	10m 17s
windows-latest 2.7	6m 18s
windows-latest 3.0	5m 39s
windows-latest 3.1	5m 27s
windows-latest 3.2	8m 27s
windows-latest ucrt	5m 50s
windows-latest mswin	3m 51s
	1h 59m 37s

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