Add basic test for the AllocationTrackerClassFileTransformer

This PR adds a very basic test for the ```AllocationTrackerClassFileTransformer```. It checks
- whether classes from the tracker packer are ignored
- whether classes with the wrong prefix are ignored
- whether the byte representation of classes are changed by the transformer
Maybe it's better to really compare contents here, since it may be that an identical copy of the byte array is returned (which would be wrong)