InDetSimEventTPCnv: Compare SiHitCollection_p3

Here we extend the unit tests for SiHitCollectionCnv_p3 to test that persistent->transient->persistent and transient->persistent->transient conversion gives consistent output for a more complicated set of SiHit objects. The current implementation of SiHitCollectionCnv_p3 does not give consistent output for persistent->transient->persistent conversion, so this part of the test is suppressed. The only consequence of this is that the SiHitCollection_p3 compression is not as good as it could be. The transient->persistent->transient shows that the output is consistent except for the localStartPosition and localStartPosition which differ due to the lossy compression used in the persistent version. In the future the test could be extended to check these values agree to some predetermined level of precision.

The level of compression will be optimized in a follow-up merge request (!70146 (merged)). At that point the commented out parts of the test will be uncommented.