ART: Make test 913-heaps more robust

Record the expected sizes of classes with GetObjectSize and replace
them with a serial to make the code robust to the Java runtime and
bitness used.

Bug: 65459070
Test: art/test/testrunner/testrunner.py -b --host -t 913
Change-Id: Iefcb7b896eee5e8b420b9b2a143c16ad15137306