Since the new baseline is Java 17, most JDKs used to run tests should have JFR support. The notable exception is OpenJ9. For that, we'll document that users should add a dependency on https://github.com/gradle/jfr-polyfill/.

Deliverables

• Move code from listeners from junit-platform-jfr to org.junit.platform.launcher.jfr package in junit-platform-launcher and register them programmatically.
• Update User Guide
• Delete junit-platform-jfr subproject