cipher: make output buffer String independent #1267

Job	Run time
openssl-1.0.2u	1m 3s
openssl-1.1.0l	1m 25s
openssl-1.1.1w	59s
openssl-3.0.15	1m 1s
openssl-3.1.7	1m 8s
openssl-3.2.3	2m 14s
openssl-3.3.2	1m 1s
openssl-3.4.0	1m 0s
openssl-master	4m 24s
libressl-3.1.5	58s
libressl-3.2.7	1m 1s
libressl-3.3.6	1m 6s
libressl-3.4.3	1m 2s
libressl-3.5.3	1m 9s
libressl-3.6.3	1m 24s
libressl-3.7.3	1m 3s
libressl-3.8.4	1m 1s
libressl-3.9.2	1m 0s
libressl-4.0.0	1m 20s
openssl-3.0.15 with fips provider	52s
openssl-3.1.7 with fips provider	1m 2s
openssl-3.2.3 with fips provider	54s
openssl-3.3.2 with fips provider	56s
openssl-3.4.0 with fips provider	1m 6s
openssl-master with fips provider	5m 8s
openssl-3.4.0 without legacy provider	1m 0s
ruby-versions / Generate Ruby versions	5s
ubuntu-22.04 2.7	1m 39s
ubuntu-22.04 3.0	59s
ubuntu-22.04 3.1	57s
ubuntu-22.04 3.2	1m 5s
ubuntu-22.04 3.3	1m 2s
ubuntu-22.04 head	1m 1s
ubuntu-22.04 truffleruby	1m 34s
ubuntu-22.04 truffleruby-head	1m 42s
ubuntu-20.04 2.7	1m 2s
ubuntu-20.04 3.0	1m 6s
ubuntu-20.04 3.1	57s
ubuntu-20.04 3.2	1m 9s
ubuntu-20.04 3.3	1m 1s
ubuntu-20.04 head	53s
ubuntu-20.04 truffleruby	1m 56s
ubuntu-20.04 truffleruby-head	1m 42s
macos-latest 2.7	50s
macos-latest 3.0	37s
macos-latest 3.1	45s
macos-latest 3.2	1m 3s
macos-latest 3.3	59s
macos-latest head	1m 2s
macos-latest truffleruby	1m 10s
macos-latest truffleruby-head	1m 40s
windows-latest 2.7	4m 46s
windows-latest 3.0	4m 37s
windows-latest 3.1	5m 16s
windows-latest 3.2	4m 12s
windows-latest 3.3	4m 47s
windows-latest head	5m 17s
windows-latest ucrt	4m 8s
windows-latest mswin	4m 5s
	1h 41m 21s

Provide feedback