[Feature Request]: Support Java 21

What would you like to happen?

Java 21 is expected to release in September, 2023.
https://www.java.com/releases/matrix/

Beam should support building Java pipelines using the Java 21 SDK.
Beam should also support running on the Java 21 runtime.

Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

Issue Components

  • Component: Python SDK
  • Component: Java SDK
  • Component: Go SDK
  • Component: Typescript SDK
  • Component: IO connector
  • Component: Beam examples
  • Component: Beam playground
  • Component: Beam katas
  • Component: Website
  • Component: Spark Runner
  • Component: Flink Runner
  • Component: Samza Runner
  • Component: Twister2 Runner
  • Component: Hazelcast Jet Runner
  • Component: Google Cloud Dataflow Runner