* Allow backwards compatibility with JUnit 4 @Rules in JUnit 5
This allows us to defer having to re-implement all of our JUnit 4 Rules as JUnit
5 extensions for now, while continuing to in-place upgrade all existing JUnit 4
test classes to JUnit 5.
As proof of concept, this upgrades PremiumListUtils (which uses AppEngineRule,
our largest and most complicated @Rule) to use the JUnit 5 test runner.
* Apply formatter to entire file
fe760d7066