Print the wavespeed that sets the CFL timestep

[BenWibking]

This modifies the timestep reduction to include the cell properties, and prints the wavespeeds (sound speed, Alfven speed, and fluid velocity) for the cell that has the minimum timestep.

When running the Orzsag-Tang problem, the output looks like this:

----> dt = 6.94e-04 (c_s = 1.00e+00, v_A = 1.78e-02, |v| = 1.86e-02)
        Timestep limited by sound speed.
cycle=27 time=1.8915349544324910e-02 dt=6.9398393409190106e-04 zone-cycles/wsec_step=2.32e+06 wsec_total=7.54e-01 wsec_step=2.83e-02

[BenWibking]

@forrestglines do you want to try this out? I think it should work, but it could use some testing.

You should be able to immediately modify it to compute and print out the temperature/sound speed, Alfven speed, and bulk velocity from the primitive vars of the timestep-limiting cell.

[BenWibking]

@pgrete Could you take a look at this?

I can also add a runtime option to turn this on/off if that would be useful.

[BenWibking]

Several of the tests fail with a CUDA memory error:

Setup complete, executing driver...

(ptr->cuda_stream_synchronize_wrapper(stream)) error( cudaErrorIllegalAddress): an illegal memory access was encountered /__w/athenapk/athenapk/external/Kokkos/core/src/Cuda/Kokkos_Cuda_Instance.cpp:165
Backtrace:

I will try to debug on the HPCC tomorrow.