Delete coverage counting backend from ccpr

This declutters the atlas generation code so there are fewer variables.
Next we will delete all the lower level rendering code and render the
atlas with stencilPath/stencilRect instead.

Bug: chromium:1158093
Change-Id: I36cff285d0f7de6f8ece4b027e62ae84aa01adc8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/380656
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
46 files changed