The `junit-platform-console-standalone` artifact available via Maven Central [1] can be used as a drop-in replacement for various other libraries listed in JUnit's 5 User Guide [2]. Included are `junit:junit:4.13.2` and also `org.hamcrest:hamcrest-core:1.3`.

This task is about to download artifact `org.junit.platform:junit-platform-console-standalone:1.8.2` and store it as `lib/junit.jar` -- and remove all traces of downloading and storing artifact `junit:junit:4.13.2`. Also, remove code for downloading and storing HamCrest artifact.

All tests in project jtreg and all tests in all other projects, including the JDK itself, should run as-is.

[1]: https://repo.maven.apache.org/maven2/org/junit/platform/junit-platform-console-standalone/
[2]: https://junit.org/junit5/docs/snapshot/user-guide/#running-tests-console-launcher