Drop JDK8 Support

[Taro L. Saito]

Current known blockers:

• AWS EMR, EMR Serverless still require JDK8 Since EMR 6.11.0 supports JDK17 https://docs.aws.amazon.com/emr/latest/EMR-Serverless-UserGuide/using-java-runtime.html
• Databricks runtime needs JDK8 https://docs.databricks.com/en/release-notes/runtime/13.3lts.html
  • Note: Spark itself supports the latest JDK
  • jdk11 can be supported by specifying JNAME environment variable https://stackoverflow.com/questions/76021747/how-to-configure-azure-databricks-cluster-to-use-java-11
    - jdk17 is also available with JNAME=zulu17-ca-amd64 environmental variable

[Taro L. Saito]

Previous attempt #2320 was failed due to these dependencies, but these problems have been solved, so it should be ok to remove JDK8 support.