Use recommended Gradle configurations instead of deprecated ones

[Rob Rudin]

marklogic-unit-test-client and marklogic-junit5 should both starting using the java-library plugin and api/implementation instead of compile/runtime.

See https://stackoverflow.com/questions/44493378/whats-the-difference-between-implementation-and-compile-in-gradle for more info.

Here's an example of a project switching to the new configurations - marklogic/ml-javaclient-util@1c53cbc

[venuiyengar]

Changed build.gradle to start using java-library plugin and changed dependencies to use api/implementation for both marklogic-unit-test-client ant marklogic-junit5