Revert "Refactor stencil clip mask generation into helper"

This reverts commit 8b3a8a5238f5be31c4408c212d867f4765e3e29a.

Reason for revert: GM assert failure

Original change's description:
> Refactor stencil clip mask generation into helper
> 
> Change-Id: If3dc80efde3b44e87ba8e7af3a258896ec5e78e6
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/288977
> Commit-Queue: Michael Ludwig <michaelludwig@google.com>
> Reviewed-by: Chris Dalton <csmartdalton@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>

TBR=bsalomon@google.com,csmartdalton@google.com,michaelludwig@google.com

Change-Id: I16559f791601145f57d147cdae345c200af313f1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/289237
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
8 files changed