Upgrade to from Java 11.0.2 to 11.0.12

The Eclipse installer does not list JustJ 11.0.2 anymore, but now lists 11.0.12. We should update our development environment setup instructions to match this. We should then also update the target platform and product to match. And any other updates to ensure we can use this Java version, although I don't expect we really need code changes for a new minor Java version.