More cleanups of Aeras tests:

- Made tests shorter so they run faster.  This is more appropriate for the test harness.
- Appended "Aeras_" to name of tests so it's easier to find these in the ctest output.
- Added regression tests to HydrostaticGaussianBallTracerInShear and XZHydrostatic.

TC3 is still failing due to a STK issue causing seg fault after solve.
I attempted to make TC4 and TCGalewsky run in parallel (to speed up the tests) and
there seems to be a similar seg fault issue.  Still looking into.