[Lilliput] Enable and fix vectorization tests

When hardcoding UseCompactObjectHeaders as enabled by default (in globals.hpp), some tests are failing:

compiler/c2/irTests/TestVectorizationMismatchedAccess.java
compiler/c2/irTests/TestVectorizationNotRun.java
compiler/loopopts/superword/TestIndependentPacksWithCyclicDependency.java

The pattern in all 3 tests is similar: they fill different types of arrays with test data, and then perform various operations and check the C2 IR whether or not vectorization kicks in. This fails with Lilliput because Lilliput throws off the alignment that those tests are implicitely expecting.