Clear and discard stencil buffers on tilers, take 2

Bug: skia:
Change-Id: I6a3bc7e50f8d4f211ed4afb2a614581b2778b27a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/245300
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
11 files changed