Add more system tests covering water tracers/isotopes

Very soon, I plan to add a one-timestep debug system test covering the tracer consistency check. Later, we should add more tests, covering at least the following (note that some of these things can be combined so that we only need a couple of tests total):

- Longer than one timestep

- Exact restart / processor / thread counts: ERP test

- Non-cold-start

- Multiple compilers

- The real isotope configuration (rather than just adding the tracers used for the tracer consistency check)

- A test that exercises dynamic landunit code, either by having a multi-year test or by having a multi-day test that turns on the for-testing daily glacier dynamics

- A test that includes FATES
- I anticipate this being an issue for total_plant_stored_h2o_col: this variable is only non-zero when using FATES, and we'll need to do something to ensure that the tracer version of this is set appropriately. There may be other biogeophysics updates in FATES for which we need to handle tracers.
- If this is non-trivial to get working, we could open a separate issue to deal with this later.