Whats in this PR?

Phase 1 of NUTCH-2887 which

1. introduces the JUnit 5 (Jupiter) dependencies including the junit-vintage-engine which allows us to run JUnit 4 tests as we gradually migrate core and plugins to JUnit 5.
2. replaces the (old) <junit> Ant task with <junitlauncher for the test-core Ant target.

Next steps

Phase 2 - core

1. Replace all JUnit 4 API usage in core tests with JUnit 5 implementations.
2. Investigate and use annotations in core tests which will reduce duplicate boilerplate and improve test filtering.

Phase 3 - core

Same as in core above but replace core with plugins.

Questions

1. Should we decompose this issue into three parts? In my opinion NUTCH-2887 Migrate to JUnit 5 Jupiter #791 ended up a mess and I would like to avoid that happening again. My proposal is therefore to merge this initial PR first. We then then merge phase 2 and finally phase 3. Any thoughts on this approach?
2. I'm going to also compile a list of out of scope nice to have items I uncover whilst working on this task.

Thanks for any comments. 👍