Add onPrePrepareDraws & createProgramInfo methods to GrDrawVerticesOp

This CL also incidentally adds:

1) a GrMeshDrawOp::Target 'outputView' virtual and switches GrOpFlushState over to overriding it.

2) a createProgramInfo helper to GrSimpleMeshDrawOpHelper

Bug: skia:9455
Change-Id: Iecd712d3ac76038651bd2e0512134e310930d527
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/274551
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
23 files changed