make bn shareable when frozen #1225

Job	Run time
openssl-1.0.2u	50s
openssl-1.1.0l	56s
openssl-1.1.1w	58s
openssl-3.0.15	1m 6s
openssl-3.1.7	1m 0s
openssl-3.2.3	58s
openssl-3.3.2	58s
openssl-3.4.0	54s
openssl-master	3m 42s
libressl-3.1.5	1m 0s
libressl-3.2.7	1m 5s
libressl-3.3.6	1m 4s
libressl-3.4.3	1m 35s
libressl-3.5.3	1m 0s
libressl-3.6.3	1m 4s
libressl-3.7.3	53s
libressl-3.8.4	1m 6s
libressl-3.9.2	1m 0s
libressl-4.0.0	1m 2s
openssl-3.0.15 with fips provider	38s
openssl-3.1.7 with fips provider	38s
openssl-3.2.3 with fips provider	38s
openssl-3.3.2 with fips provider	38s
openssl-3.4.0 with fips provider	45s
openssl-master with fips provider	3m 31s
openssl-3.4.0 without legacy provider	1m 1s
ruby-versions / Generate Ruby versions	3s
ubuntu-22.04 2.7	1m 2s
ubuntu-22.04 3.0	58s
ubuntu-22.04 3.1	1m 0s
ubuntu-22.04 3.2	1m 2s
ubuntu-22.04 3.3	58s
ubuntu-22.04 head	57s
ubuntu-22.04 truffleruby	1m 40s
ubuntu-22.04 truffleruby-head	1m 42s
ubuntu-20.04 2.7	58s
ubuntu-20.04 3.0	56s
ubuntu-20.04 3.1	1m 2s
ubuntu-20.04 3.2	1m 2s
ubuntu-20.04 3.3	1m 0s
ubuntu-20.04 head	55s
ubuntu-20.04 truffleruby	1m 29s
ubuntu-20.04 truffleruby-head	1m 34s
macos-latest 2.7	51s
macos-latest 3.0	38s
macos-latest 3.1	40s
macos-latest 3.2	37s
macos-latest 3.3	41s
macos-latest head	39s
macos-latest truffleruby	59s
macos-latest truffleruby-head	1m 1s
windows-latest 2.7	5m 49s
windows-latest 3.0	4m 24s
windows-latest 3.1	4m 13s
windows-latest 3.2	4m 45s
windows-latest 3.3	4m 41s
windows-latest head	4m 29s
windows-latest ucrt	3m 33s
windows-latest mswin	2m 26s
	1h 28m 44s

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