RFR: 8039489: Refactor test framework for dynamic VM options

[Dmitry Fazunenko]

Hi,

Would you please look at the new version of a common library for testing 
dynamic VM options.

Description:
Some time ago a library for testing VM flags which could be changed 
dynamically was integrated into the hs repository:
test/testlibrary/com/oracle/java/testlibrary/DynamicVMOptionChecker.java
test/testlibrary/com/oracle/java/testlibrary/TestDynamicVMOption.java

The library was designed in not the most optimal way.
This change is an attempt to redesign it:

   test/testlibrary/com/oracle/java/testlibrary/DynamicVMOption.java

is a new version which provides a convenient access to the HS API on 
changing VM flags.
The tests based on the library are also refactored to meet new API.

You comments will be much appreciated.

http://cr.openjdk.java.net/~ehelin/dmitry/8039489/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8039489

I want to thank Erik Helin for his incredible assistance with working on 
this change.

Thanks,
Dima