RFR(S) : 8252477 : nsk/share/ArgumentParser should expect that jtreg "splits" an argument

[Igor Ignatyev]

http://cr.openjdk.java.net/~iignatyev//8252477/webrev.00/
> 99 lines changed: 19 ins; 20 del; 60 mod; 

Hi all,

could you please review the patch which unblocks the rest of 8219140's (get rid of vmTestbase/PropertyResolvingWrapper) sub-tasks?

background from JBS:
> jtreg splits command line by space to get the list of arguments and there is no way to prevent that (nor thru escaping, nor by adding quotes). currently, PropertyResolvingWrapper handles that and joins multiple arguments within double quotes into one argument before passing it to the actual test class. the only place where it's needed is in the tests which use nsk/share/ArgumentParser (or more precisely nsk.share.jpda.DebugeeArgumentHandler and nsk/share/jdb/JdbArgumentHandler). 
> 
> in preparation for PropertyResolvingWrapper removal, ArgumentParser should be updated to handle the "split" argument on its own.

I've also taken the liberty to slightly clean up ArgumentParser.

JBS: https://bugs.openjdk.java.net/browse/JDK-8252477
webrev: http://cr.openjdk.java.net/~iignatyev//8252477/webrev.00/
testing: all the tests which use ArgumentParser (:vmTestbase_nsk_aod :vmTestbase_nsk_jdb :vmTestbase_nsk_jdi :vmTestbase_nsk_jdw ,:vmTestbase_nsk_jvmti :vmTestbase_vm_compiler :vmTestbase_vm_mlvm) on {windows,linux,macos}-x64

Thanks,
-- Igor