Avoid RAII wrappers around PatchWriter

Instead of CubicPatch(writer) << control points ... code now writes
writer << Cubic(controlPoints). The main benefit of this is that the
control points are available to the PatchWriter. This allows it (in
follow up CLs) to automatically chop the curves and track the last join
control point.

Change-Id: I38b57a141261afd42e511cc195eb5e64a2382263
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/501837
Reviewed-by: Christopher Dalton <csmartdalton@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
8 files changed