RFR: 8235530: Removed duplicated threadByName methods in nsk/jdi tests

[Leonid Mesnik]

Hi

Could you please review following fix which just remove duplicated 
threadByName methods and JDITestRuntimeException exceptions in nsk/jdi 
tests. I don't see any reason to have so many copies of them.

The method threadByName is added nsk.share.jdi.Debugee class as 
'threadByNameOrThrow' because slightly different 'threadByName' already 
exist there. I filed another sub-task 
https://bugs.openjdk.java.net/browse/JDK-8235544 to review usage and 
merge these 2 methods later.

This fix affects about ~4000 lines and I want to keep it as 
straight-forward as possible.

webrev: http://cr.openjdk.java.net/~lmesnik/8235530/webrev.00/

bug: https://bugs.openjdk.java.net/browse/JDK-8235530

The next planned steps are in:

https://bugs.openjdk.java.net/browse/JDK-8233830

Leonid