[VECGEOM-393] Trapezoid unit test and benchmark improvements after bug investigation

This commit expands test cases, to include the topology from JIRA issue VECGEOM-393 into Trapezoid unit test and benchmark.

As far as I can tell, there is no bug inside the VecGeom trapezoid code. All tests are successful, in particular, the new trapezoid topology including non-zero Alpha1,Alpha2 (see ./TrapezoidBenchmark -type 2) shows perfect agreement between VecGeom and Geant4 trapezoids.

As noted by Evgueni in a comment for VECGEOM-393, the bug probably comes from the caller of VecGeom's trapezoid -- it is not clear whether this caller is Geant4 (through some kind of construction delegation between UTrap and VecGeom's trapezoid constructors) -- or whether Evgueni's tests were independent of Geant4.

Anyway, I expect this commit to pass all Jenkins tests, and as such I believe it should be merged.