Revert "Add store_masked to RasterPipeline and the builder."

This reverts commit cf6d9eedd8fba3dc56011d2968b6e5edce25c6bb.

Reason for revert: dm failures

Original change's description:
> Add store_masked to RasterPipeline and the builder.
>
> For now, we compute the full mask `dr & dg & db` every time
> store_masked is called. This will probably get a dedicated
> register later.
>
> Change-Id: I87a28def28795a3b352b2069b96a4d934c396e3e
> Bug: skia:13676
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/607776
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
> Auto-Submit: John Stiles <johnstiles@google.com>

Bug: skia:13676
Change-Id: I779c8b8d14e39ff8fa7ff206cd4bd3dc52fe186f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/608176
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Tyler Denniston <tdenniston@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
6 files changed