Add support for 1979-PD needed for some CAM resolutions

[ekluzek]

For very high resolutions we don't want to support large transient landuse.timeseries datasets for the complete 1850-2100 time series. As such we'd like to add an option that for 1979 (because that is where CAM starts it's HIST compsets) to Present Day (PD). Where PD will be moving forward as time goes on. SSP2-4.5 will be used for the future scenario data for the years after the historical that we have (for CMIP6 that's till 2015). When CMIP7 comes online in a year or two the data will likely go to something like 2024, and we'll then make PD something like 2030 so that the present time can continue to move forward similar to now. For now because we know about the CMIP7 update we'll have datasets that go to 2026. This issue is closely tied to #2487

This will mean adding a 1979-PD_transient use case. CLM compsets for these resolutions should set this use-case using the "grid" attribute to the setting in config_component.xml.

[ekluzek]

In meeting with @slevis-lmwg we realized that this should also change the naming convention for the fsurdata land-use timeseries files. So that should be part of this as well.

[slevis-lmwg]

In meeting with @slevis-lmwg we realized that this should also change the naming convention for the fsurdata land-use timeseries files. So that should be part of this as well.

Link to the conversation about this, where we decided the fsurdat files need to use a similar naming algorithm as the landuse files:

• "hist" before 2016
• "ssp" after 2015