Revert "Clear and discard stencil buffers on tilers"

This reverts commit 7b2c85577d79bf1bda6b57d9af8ad793e2fc4862.

Reason for revert: nanobench hangs on chromebook bots during mipmap regeneration

Original change's description:
> Clear and discard stencil buffers on tilers
>
> Bug: skia:
> Change-Id: I42e99cb75567825ac7751fc0ec56e4c45132628b
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210425
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Chris Dalton <csmartdalton@google.com>

TBR=egdaniel@google.com,robertphillips@google.com,csmartdalton@google.com

Change-Id: I69e04c4797b6bde934d86c83bf0348c8abadcfc3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/213824
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
16 files changed