Add unit test for get_climatology_info flow.cylc utility

[ceblanton]

Currently, get_climatology_info is a python utility that forms the climatology-related task graphs and task definitions, via Jinja2 templating:

{{ config | get_climatology_info('task-graph') }}
{{ config | get_climatology_info('task-definitions') }}

While E2E functionality is tested elsewhere, functionality for this subtool needs to be ensured. This issue tracks the development of a pytest unit test to verify the creation of climatology task graphs and definitions.

An example could be:

1. Create 5 year climatology with 1-year timeseries chunks
2. Create 4 year climatology with 2-year timeseries chunks