- Update google-java-format to a version compatible with JDK 21 and run "gw spotlessApply".
- Fix wrong test assumption
JavaCodeGenerator writes a properties file using java.util.Properties,
which doesn't guarantee order of entries.
- Fix most deprecation warnings
- Add CI job for JDK 21
This change activates the `TYPESAFE_PROJECT_ACCESSORS` feature
preview in Gradle, and switches to such accessors instead of
string-based project references, where possible
Relates-To: apple/pkl#204
Signed-off-by: Sam Gammon <sam@elide.ventures>