Reland "Delete the index buffer from middle-out tessellation"

This is a reland of 0d0b1b3b56da6d13506d34756c79a79c4929950f

Original change's description:
> Delete the index buffer from middle-out tessellation
>
> This gives us more flexibility for customizing triangulations in
> future modes. It is also hopefully cheaper than the extra memory
> indirection from indexed draws.
>
> Bug: skia:10419
> Bug: chromium:1202607
> Change-Id: Iba41a35a634edf8f962c3d604c7e035e7a85801d
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/407296
> Commit-Queue: Chris Dalton <csmartdalton@google.com>
> Reviewed-by: Greg Daniel <egdaniel@google.com>

Bug: skia:10419
Bug: chromium:1202607
Change-Id: I2f5022d2122dee1ca197780b534663b37cd2504f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/408236
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
11 files changed