Revert "Decouple SkMesh from Ganesh backend"

This reverts commit e2e5b841e92bb80da627ceab414d17af4542a38f.

Reason for revert: G3 IWYU

Original change's description:
> Decouple SkMesh from Ganesh backend
>
> This involves moving SkMesh::MakeIndexBuffer,
> SkMesh::CopyIndexBuffer, SkMesh::MakeVertexBuffer, and
> SkMesh::CopyVertexBuffer to a new SkMeshes namespace.
>
> There are versions that take in a GrDirectContext* for the
> Ganesh backend and the ones that don't are for the CPU backend.
>
> Change-Id: Iaa12871d2b66fbdfa8a35a52f89d800563be6df0
> Bug: skia:14317
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/721899
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Kevin Lubick <kjlubick@google.com>

Bug: skia:14317
Change-Id: Ibff09b44d395c60a9ad490a55fed9a06fd6a93c3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/724036
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
16 files changed