Hammer chart shows min/mean/median/max for each set of requests

[SteveDesmond-ca]

As a SRE, I want to see more detail about how my app reacts to a being hammered, so that I can better optimize its performance.

Acceptance criteria:

• chart output after a hammer command contains 4 lines: min, mean, median, max
• each line is a different color (green, yellow, orange, red? blue, green, yellow/orange, red?)
• chart contains a legend for which color is which

Implementation notes:

• min/mean/median/max should probably be encapsulated in a Aggregate/Metrics class/struct
• generics would likely make implementation easier (switch on T being a single double (:smirk_cat:) vs Aggregate/Metrics

[SteveDesmond-ca]

This may be blocked on beto-rodriguez/LiveCharts2#144, as I don't know if the chart will be clear enough without a legend...

[SteveDesmond-ca]

New Stats class, including Min/Mean/Median/Max, has been added and Hammer now uses that in its results.

The multiline branch includes work-in-progress for the new MultilineChart, but needs a legend before it can be merged.

beto-rodriguez/LiveCharts2#310 has been opened as a potential initial path forward.

[SteveDesmond-ca]

At this point, forking LiveCharts and pulling out just the SkiaSharp functionality might be the best bet...

[SteveDesmond-ca]

Waiting around for LiveCharts to support this paid off, as this has been implemented and will be released in the next version.