RFR(S): 8171090: Convert VMStruct_test to GTest

[Kirill Zhaldybin]

Dear all,

Could you please review this fix for 8171090?

I added accessors to get arrays' lengths since they were defined in cpp 
file and separated the test into to two scenarios.

WebRev: http://cr.openjdk.java.net/~kzhaldyb/webrevs/JDK-8171090/webrev.00/
CR: https://bugs.openjdk.java.net/browse/JDK-8171090

Thank you.

Regards, Kirill