Reduce memory requirements of tests

[Aariq]

The long-running tests currently skipped by default are causing my R session to run out of memory. A fix might be as simple as breaking these into separate tests, but it might also be good to see if all unit tests can be made more minimal.

[Aariq]

This test in particular seems to be huge:

  some_data <- npn_download_status_data(
    request_source = "Unit Test",
    years = 2013,
    class_ids = c(15), #TODO pick a smaller class or year with less data!
    additional_fields = c("Class_ID")
  )

Could write to disk (as one would do in practice), pick a smaller class, and/or pick a year with less data.