Revert "Stack-allocate pipelines for GrMeshDrawOp"

This reverts commit dfe5000a5ff2cabb50ddc139882dc1f3005fa429.

Reason for revert: HWAA pipeline flag not getting set for dashing.

Original change's description:
> Stack-allocate pipelines for GrMeshDrawOp
> 
> Stack-allocates the pipelines in onExecute. This saves us from having
> to store the pipelines on the heap, as well as delaying the need to
> detach processors until onExecute. The delay is an improvement because
> it allows us to keep visiting proxies after onPrepare. (Previously,
> they were moved out of GrProcessorSet and into a pipeline during
> onPrepare, so visiting proxies was impossible after that point.)
> 
> Bug: skia:8731
> Change-Id: Idc05063fb0dfbfed42b434e429fa5a497097bdae
> Reviewed-on: https://skia-review.googlesource.com/c/193368
> Commit-Queue: Chris Dalton <csmartdalton@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>

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

Change-Id: If706f19423310846de70288f393ac12f17ffeee5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:8731
Reviewed-on: https://skia-review.googlesource.com/c/195161
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
30 files changed