Remove usage of IO internals. #700

Job	Run time
openssl-1.0.2u	2m 40s
openssl-1.1.0l	2m 3s
openssl-1.1.1t	2m 24s
openssl-3.0.8	3m 53s
libressl-3.1.5	2m 33s
libressl-3.2.7	2m 38s
libressl-3.3.6	2m 36s
libressl-3.4.3	3m 18s
libressl-3.5.3	3m 32s
libressl-3.6.1	3m 11s
libressl-3.7.0	3m 9s
openssl-3.0.8 fips	4m 52s
ruby-versions / Generate Ruby versions	2s
ubuntu-22.04 2.6	1m 6s
ubuntu-22.04 2.7	57s
ubuntu-22.04 3.0	46s
ubuntu-22.04 3.1	59s
ubuntu-22.04 3.2	47s
ubuntu-22.04 head	46s
ubuntu-22.04 truffleruby	1m 7s
ubuntu-22.04 truffleruby-head	1m 18s
ubuntu-20.04 2.6	1m 1s
ubuntu-20.04 2.7	55s
ubuntu-20.04 3.0	59s
ubuntu-20.04 3.1	49s
ubuntu-20.04 3.2	1m 0s
ubuntu-20.04 head	49s
ubuntu-20.04 truffleruby-head	3m 0s
macos-latest 2.6	1m 45s
macos-latest 2.7	1m 34s
macos-latest 3.0	1m 0s
macos-latest 3.1	1m 15s
macos-latest 3.2	2m 24s
macos-latest head	1m 0s
macos-latest truffleruby-head	2m 39s
windows-latest 2.6	6m 14s
windows-latest 2.7	6m 31s
windows-latest 3.0	5m 45s
windows-latest 3.1	5m 15s
windows-latest 3.2	6m 34s
windows-latest ucrt	4m 52s
windows-latest mswin	3m 21s
	1h 43m 19s

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