[HeapViewer] Incorrect object array size

[thurka]

Steps to reproduce:

1. run VisualVM with -J-Dorg.graalvm.visualvm.lib.jfluid.heap.level=100
2. open attached heapdump from Substrate VM heapdump-1693551770802.hprof.gz
3. the log file conains the following log. See below.
4. inspect heap dump and discover that object arrays are roughly twice as big

CONFIG [org.graalvm.visualvm.lib.jfluid.heap.ObjectSizeSettings]: MinimumInstanceSize set to 24
CONFIG [org.graalvm.visualvm.lib.jfluid.heap.ObjectSizeSettings]: OopSize uses idSize 8
CONFIG [org.graalvm.visualvm.lib.jfluid.heap.ObjectSizeSettings]: OopSize computed as 16

The log shows that the oopSize is computed as 16, but it should be 8.

[thurka]

Fixed in master.