Several fixes to global plots

[xylar]

This merge fixes:

• the spacing for the two-line control title in global main vs. control plots
• the spacing of stats (min, max, mean, corr, etc.) for numbers in exponential notation
• the format of units for mass fluxes

To better test these fixes, the suites have been updated so the "main" run in the main_vs_ctrl test use year 8 as the end year, rather than 10 in the "control" run. Since Hovmoller plots don't work with different time bounds, these have been disabled in the main_vs_ctrl test.

Checklist

• Testing comment in the PR documents testing used to verify the changes

Fixes #1135

[xylar]

Testing

I successfully ran the developer suite. Results are here:
https://web.lcrc.anl.gov/public/e3sm/diagnostic_output/xasaydavis/analysis_testing/chrysalis/fix-control-global-subtitle-spacing/

[xylar]

Here's an example image showing the fixes: