RFR (S) 8252215: Remove VerifyOptoOopOffsets flag

[Aleksey Shipilev]

RFE:
   https://bugs.openjdk.java.net/browse/JDK-8252215

VerifyOptoOopOffsets flag does not seem to be used (no tests in the current test base), and it does 
not seem to work reliably (see JDK-4834891). It might be a good time to remove it. JDK-4834891 
evaluation says: "The flag VerifyOptoOopOffsets has not been valid since the introduction of 
sun/misc/Unsafe and the flag should not be used for general testing."

How about we remove it?
   https://cr.openjdk.java.net/~shade/8252215/webrev.01/

Testing: tier1 (locally); jdk-submit (still running?)

-- 
Thanks,
-Aleksey