Feature request: Include reanalysis with Pre-Industrial period coverage

[chengzhuzhang]

A feature request from @wlin7: for the interest of coupled model auto-tuning, on variables like TAS, U200 of PI condition, we would like to include reanalysis that cover PI period. One such product is NOAA's 20th Century Reanalysis (20CRv3). Eventually looking to add PI comparison into e3s_diags. Need to first process the data into format that used by e3sm_diags, then add related variables to the plot list.