**Problem**
Running sbt 2.x with JDK 8 produces a confusing "server was not
detected" error because the JDK version check only required JDK 8+
and only ran in the non-native-client path.
**Solution**
Move java_version detection before the native client decision and add
checkJava17ForSbt2 that requires JDK 17+ when sbt major version >= 2.
Fixes#8813
Co-authored-by: Dream <42954461+eureka928@users.noreply.github.com>