Revert changes that depend on Java 11+
Revert changes that depend on Java 11+

In Java 8, neither `private` nor `public static` methods are allowed on interfaces. Making these few changes makes it possible to compile cwLjava on Java 8 once again.

Co-authored-by: John Didion <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@didion.net>
common-workflow-language/schema_salad,common-workflow-language/schema_salad,common-workflow-language/schema_salad,common-workflow-language/schema_salad,common-workflow-language/schema_salad,common-workflow-language/schema_salad,common-workflow-language/schema_salad