Remove usage of IO internals. #717

Job	Run time
openssl-1.0.2u	2m 53s
openssl-1.1.0l	2m 26s
openssl-1.1.1t	2m 24s
openssl-3.0.8	4m 16s
libressl-3.1.5	3m 16s
libressl-3.2.7	3m 7s
libressl-3.3.6	4m 1s
libressl-3.4.3	3m 1s
libressl-3.5.3	3m 17s
libressl-3.6.1	3m 11s
libressl-3.7.0	3m 11s
openssl-3.0.8 fips	4m 47s
ruby-versions / Generate Ruby versions	2s
ubuntu-22.04 2.6	1m 13s
ubuntu-22.04 2.7	1m 10s
ubuntu-22.04 3.0	1m 10s
ubuntu-22.04 3.1	1m 28s
ubuntu-22.04 3.2	1m 10s
ubuntu-22.04 head	1m 7s
ubuntu-22.04 truffleruby	57s
ubuntu-22.04 truffleruby-head	1m 10s
ubuntu-20.04 2.6	1m 15s
ubuntu-20.04 2.7	1m 18s
ubuntu-20.04 3.0	1m 21s
ubuntu-20.04 3.1	1m 12s
ubuntu-20.04 3.2	1m 17s
ubuntu-20.04 head	1m 4s
ubuntu-20.04 truffleruby-head	1m 12s
macos-latest 2.6	1m 57s
macos-latest 2.7	1m 47s
macos-latest 3.0	2m 15s
macos-latest 3.1	1m 28s
macos-latest 3.2	1m 24s
macos-latest head	1m 30s
macos-latest truffleruby-head	2m 25s
windows-latest 2.6	5m 59s
windows-latest 2.7	5m 40s
windows-latest 3.0	5m 27s
windows-latest 3.1	6m 28s
windows-latest 3.2	6m 17s
windows-latest ucrt	5m 22s
windows-latest mswin	3m 1s
	1h 48m 56s

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