Revert "added skeletal animation support to GPU backend"

This reverts commit b6307340e8a6a9d3a7517def7f5eaaadffd07d14.

Reason for revert: patch/atlas failing in gold

Original change's description:
> added skeletal animation support to GPU backend
> 
> added caching of SkVertices
> 
> Docs-Preview: https://skia.org/?cl=138596
> Bug: skia:
> Change-Id: Ia750f55f5f6d0de250d9e9c5619f4d1ac856f9f5
> Reviewed-on: https://skia-review.googlesource.com/138596
> Reviewed-by: Brian Osman <brianosman@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Commit-Queue: Ruiqi Mao <ruiqimao@google.com>

TBR=robertphillips@google.com,brianosman@google.com,reed@google.com,ruiqimao@google.com

Change-Id: Idfaf016a7ff4cdd8af2543d510706f489d04417a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/139281
Reviewed-by: Ruiqi Mao <ruiqimao@google.com>
Commit-Queue: Ruiqi Mao <ruiqimao@google.com>
28 files changed