Swell workflows for common comparisons

[ashiklom]

Two common use cases (but there may be others):

• Compare two different sets of pinned versions of JEDI
• Compare two different versions of GEOS

Each of these comparisons would probably be separate workflows (e.g., swell create compare_jedi; swell create compare_geos).

Key to these workflows is not only making sure that both workflows execute without error, but also to calculate relevant comparison diagnostics (e.g., absolute diffs; maybe some maps / time series).