Revert Ubuntu 22.04/ JDK8-removal changes for stable 2.346

[dduportal]

(twin of #252) The PR #249 should not have been raised and merged as JDK8 should still be used to build this version line.

The current PR only rollbacks the changes related to JDK8/Ubuntu but keep the rest (doc, chores, etc.).

• jenkins-infra/docker-packaging@2.1.9...2.1.32
• Reverted the openssl command (related to Ubuntu 22.04) change
• Reverted the java bin path for spawning the inbound agent

$ docker run --rm -ti --entrypoint=openssl jenkinsciinfra/packaging:2.1.32 pkcs12 --help 2>&1 | grep legacy
$ docker run --rm -ti --entrypoint=openssl jenkinsciinfra/packaging:2.1.41 pkcs12 --help 2>&1 | grep legacy
 -legacy             Use legacy encryption: 3DES_CBC for keys, RC2_CBC for certs
$ docker run --rm -ti --entrypoint=/opt/jdk-11/bin/java jenkinsciinfra/packaging:2.1.32 -version                        
openjdk version "11.0.13" 2021-10-19
OpenJDK Runtime Environment Temurin-11.0.13+8 (build 11.0.13+8)
OpenJDK 64-Bit Server VM Temurin-11.0.13+8 (build 11.0.13+8, mixed mode)
$ docker run --rm -ti --entrypoint=/opt/jdk-8/bin/java jenkinsciinfra/packaging:2.1.32 -version
openjdk version "1.8.0_312"
OpenJDK Runtime Environment (Temurin)(build 1.8.0_312-b07)
OpenJDK 64-Bit Server VM (Temurin)(build 25.312-b07, mixed mode)