[graphite] Add SparseStrips RenderSteps

* Adds the EndCap and WideTile rendersteps

* Mostly cosmetic change, the actual code path in drawGeometry will be added in the future.

Bug: b/466122293
Bug: b/466119734
Bug: b/385170952
Change-Id: I6f930d5f80471ffd3e3d6e23ea981922d9c599e3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1338156
Commit-Queue: Thomas Smith <thomsmit@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>