[11u]: RFR(S): 8232370: Refactor some com.sun.jdi tests to enable IDE integration

[Langer, Christoph]

Hi,

please review this backport of a test-only change to better support JDK11 development in the Eclipse IDE. The Original change applies cleanly for 2 files but test/jdk/com/sun/jdi/RedefineImplementor.java does not exist in 11u, so I simply dropped this part.

Bug: https://bugs.openjdk.java.net/browse/JDK-8232370
Original Change: https://hg.openjdk.java.net/jdk/jdk/rev/5f14a659a8cb
Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8232370.11u/

Thanks
Christoph