Detect calendar of model runs automatically

CMEW currently requires the user to specify the calendar for each model run. This is not something that the user will always know, and will need to find out for each run. It is also not something that they need to provide for AutoAssess, so would be a hurdle in the transition from AutoAssess to CMEW. The calendar of the simulation can be determined from the PP metadata.

The calendar is needed solely as input to CDDS, so step 1 is to discuss with the CDDS team what alternative routes could be available. Does/could CDDS allow calendar to be auto-detected from the data? If not, does CDDS already check consistency between the specified calendar and the value in the PP metadata?

Start by discussing with the CDDS team whether calendar values can be detected from PP metadata, and whether CDDS checks the specified calendar against that metadata. Confirm the available route before locating the CMEW workflow change. Done means the CDDS behavior and an implementation path for removing the user's calendar input are documented.

Written by the indexing model from the issue text.