Add two new tests that run subset_data and then run a case from it

[ekluzek]

We need to add a new test (to either the test/tools or to aux_clm test suite) that runs subset_data to create data files and then creates a case from it and runs the case. This way we can keep the subset_data workflow working as we make changes to it.

[ekluzek]

Another part of this should be to subset the DATM data and then run a case from it. This was first discussed here:

#2356 (comment)

[samsrabin]

At least two tests should be added, for point and regional subsets. Both tests should use all the --create- options to subset_data.