Add performance check

[forsyth2]

Add example run configuration to debug performance issues described at E3SM-Project/zppy#694 (comment).

[forsyth2]

I had to remove the extra 2 log lines from the output. We should definitely prioritize #10 to make parsing logs easier.

[forsyth2]

09:27:49 Begin computing globalAnnual for TREFHT, FSH
09:28:35 Begin plotting TREFHT glb
09:28:36 Begin plotting FSH glb
09:28:38 Begin computing northern hemisphere average for TREFHT, FSH
09:29:13 Begin plotting TREFHT n
09:29:14 Begin plotting FSH n
09:29:16 Begin computing southern hemisphere average for TREFHT, FSH
09:29:50 Begin plotting TREFH s
09:29:51 Begin plotting FSH s
09:29:54 Create Viewers
09:29:54 Done

Summary table (seconds):

Action	glb	n	s
Compute averages for both variables	47	35	34
Plot TREFHT	1	1	1
Plot FSH	2	2	3

[forsyth2]

@chengzhuzhang noted the following in E3SM-Project/zppy#694 (comment):

Roughly, 2 hours are use for computation and more than 4 and half hours are used in plotting line plots. I think we should be able to save time at least on plotting.

This seems to disagree with my time data from this extremely minimal example, where by far the greatest amount of time is spent on computing the averages.

If it is the plotting slowing things down, a couple ideas:

• There is a tall call hierarchy of plotting functions. Maybe there's too much function call overhead? I can't imagine that actually being the issue though.
• We're saving plots to both single image PNGs and to a combined PDF (even for the viewers, there's a PDF created of n pages, 1 for each plot). Maybe the PDF concatenation scales poorly?