Update GrPathTessellator::prepare() to take a list of paths

This allows us to batch multiple paths together in a single
tessellation. The first user will be the atlas, but the convex
renderer is also a good candidate.

Bug: skia:12258
Change-Id: I4d415d32bbf423cfd9b7ddf2543c21371936da90
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/433776
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
13 files changed