RFR: 8252656: Replace RegisterArrayForGC mechanism with plain Handles

[Stefan Karlsson]

Hi all,

Please review this patch to replace the RegisterArrayForGC mechanism 
with the usage of plain Handles.

https://cr.openjdk.java.net/~stefank/8252656/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8252656

JVM_GetStackAccessControlContext collects a bunch of oops in array and 
then calls into allocating code that might safepoint. To deal with this, 
the local array is registered and explicitly visited by the GCs. This 
patch gets rid of this and use an array of Handles instead.

I've tested this locally with test TEST="test/jdk/java/security". Any 
other suggestions on what to test this with? I've also run this through 
tier1, as a sanity check.

Thanks,
StefanK