RATIS-2121. Set javac --release when compiling with JDK 9+

[adoroszlai]

What changes were proposed in this pull request?

Java 9 introduced new javac option --release, which helps ensure compatibility with the given Java version (blog with great explanation). The goal of this change is to set this option when compiling with JDK 9+, instead of --source and --target.

--release expects version without the old-style 1. prefix (i.e. 8 instead of 1.8). maven-enforcer-plugin added support for the same in version 3.2.1, so we also need to bump the plugin.

https://issues.apache.org/jira/browse/RATIS-2121

How was this patch tested?

Compiled Ratis with JDK versions 8, 11, 17, targeting versions up to that of the JDK. Verified class file version.

for target in 8 11 17; do
  major=$(( target + 44 ))
  for jdk in 8 11 17; do
    if [[ $jdk -lt $target ]]; then break; fi
    JAVA_HOME=/usr/lib/jvm/java-${jdk}-openjdk-amd64 mvn -B -V -DskipTests clean package -Djavac.version=${target}
    javap -verbose ratis-common/target/classes/org/apache/ratis/RaftConfigKeys.class | grep "major version: $major"
  done
done

CI:
https://github.com/adoroszlai/ratis/actions/runs/9722037600

[szetszwo]

+1 the change looks good.

[adoroszlai]

Thanks @szetszwo for the review.