filter 0 counts from pie chart colors

[tlugger]

Fixes #72

The pie chart could have mismatched colors when some test conclusion types had 0 counts (e.g., no failures or no skips)

Creates consistent sequential pie indicies in renderer.ts

[robherley]

hey @tlugger, thanks for the contribution!

i'm not entirely convinced this was the failure mode, given the screenshot in #72 showed at least one test for each slice of the pie

also running the newly added tests (without the changes) still passes on main 😆