Remove testing headers from benchmarking

The code in vtkm/cont/Testing.h now requires a library, which is not built if testing is not built. Thus, the benchmarking code was giving a compile error if benchmarking was on but testing was off.

Change the benchmarking to not rely on anything in the Testing framework. This means using classes in vtkm/source instead of MakeTestData. Also avoid using the TestValue defined for the tests. (In one case, we have a simple replacement.) Also had to fix a problem with a header file not defining everything it needed to compile.